diff --git a/src/4.3_to_5.0/__test_resources__/addLegacyBookmarkToUIFolder.ts b/src/4.3_to_5.0/__test_resources__/addLegacyBookmarkToUIFolder.ts
new file mode 100644
index 0000000..464db15
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/addLegacyBookmarkToUIFolder.ts
@@ -0,0 +1,62 @@
+import { ContentRecord } from "@activeviam/activeui-sdk-5.1";
+import { produce } from "immer";
+
+/**
+ * Returns a new `legacyUIFolder` with the given `legacyBookmarksToAdd` added.
+ * Useful for creating legacyUIFolders for tests.
+ * Does not mutate `legacyUIFolder`.
+ */
+export function addLegacyBookmarkToUIFolder(
+  legacyUIFolder: ContentRecord,
+  legacyBookmarksToAdd: { [id: string]: any },
+): ContentRecord<any, "response"> {
+  const content = legacyUIFolder.children?.bookmarks.children?.content;
+  const structure = legacyUIFolder.children?.bookmarks.children?.structure;
+
+  if (!content || !structure) {
+    throw new Error(
+      "Expected `legacyUIFolder` to contain the `content` and `structure` properties. Please ensure these properties exist",
+    );
+  }
+
+  return produce(legacyUIFolder, (draftFolder) => {
+    const existingBookmarks =
+      draftFolder.children!.bookmarks.children!.content!.children || {};
+
+    // Add the bookmark content
+    draftFolder.children!.bookmarks.children!.content!.children = {
+      ...existingBookmarks,
+      ...legacyBookmarksToAdd,
+    };
+
+    const keysOfBookmarksToAdd = Object.keys(legacyBookmarksToAdd);
+
+    const bookmarkStructureToAdd = keysOfBookmarksToAdd.reduce(
+      (acc: { [key: string]: ContentRecord }, key: string) => {
+        const bookmarkEntry = legacyBookmarksToAdd[key].entry;
+        acc[key] = {
+          entry: {
+            isDirectory: true,
+            owners: bookmarkEntry.owners,
+            readers: bookmarkEntry.readers,
+            timestamp: 1607879735685,
+            lastEditor: "admin",
+            canRead: true,
+            canWrite: true,
+          },
+        };
+        return acc;
+      },
+      {},
+    );
+
+    const existingStructure =
+      draftFolder.children!.bookmarks.children!.structure!.children || {};
+
+    // Add the bookmark structure
+    draftFolder.children!.bookmarks.children!.structure!.children = {
+      ...existingStructure,
+      ...bookmarkStructureToAdd,
+    };
+  });
+}
diff --git a/src/4.3_to_5.0/__test_resources__/emptyLegacyUIFolder.ts b/src/4.3_to_5.0/__test_resources__/emptyLegacyUIFolder.ts
new file mode 100644
index 0000000..5243ecd
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/emptyLegacyUIFolder.ts
@@ -0,0 +1,214 @@
+/**
+ * Contains an empty /ui folder of a Content Server, useful for injecting content to be used in unit tests.
+ */
+export const emptyLegacyUIFolder = {
+  entry: {
+    isDirectory: true,
+    owners: ["admin"],
+    readers: ["admin"],
+    timestamp: 1607879725132,
+    lastEditor: "admin",
+    canRead: true,
+    canWrite: true,
+  },
+  children: {
+    bookmarks: {
+      entry: {
+        isDirectory: true,
+        owners: ["ROLE_CS_ROOT"],
+        readers: ["ROLE_USER"],
+        timestamp: 1607879735685,
+        lastEditor: "admin",
+        canRead: true,
+        canWrite: true,
+      },
+      children: {
+        content: {
+          entry: {
+            isDirectory: true,
+            owners: ["ROLE_USER"],
+            readers: ["ROLE_USER"],
+            timestamp: 1607879735685,
+            lastEditor: "admin",
+            canRead: true,
+            canWrite: true,
+          },
+          children: {},
+        },
+        i18n: {
+          entry: {
+            isDirectory: true,
+            owners: ["ROLE_CS_ROOT"],
+            readers: ["ROLE_USER"],
+            timestamp: 1607879735685,
+            lastEditor: "admin",
+            canRead: true,
+            canWrite: true,
+          },
+          children: {
+            "en-US": {
+              entry: {
+                isDirectory: true,
+                owners: ["ROLE_CS_ROOT"],
+                readers: ["ROLE_USER"],
+                timestamp: 1607879735685,
+                lastEditor: "admin",
+                canRead: true,
+                canWrite: true,
+              },
+            },
+            "fr-FR": {
+              entry: {
+                isDirectory: true,
+                owners: ["ROLE_CS_ROOT"],
+                readers: ["ROLE_USER"],
+                timestamp: 1607879735685,
+                lastEditor: "admin",
+                canRead: true,
+                canWrite: true,
+              },
+            },
+          },
+        },
+        structure: {
+          entry: {
+            isDirectory: true,
+            owners: ["ROLE_USER"],
+            readers: ["ROLE_USER"],
+            timestamp: 1607879735685,
+            lastEditor: "admin",
+            canRead: true,
+            canWrite: true,
+          },
+          children: {},
+        },
+      },
+    },
+    settings: {
+      entry: {
+        isDirectory: true,
+        owners: ["ROLE_CS_ROOT"],
+        readers: ["ROLE_USER"],
+        timestamp: 1607879735685,
+        lastEditor: "admin",
+        canRead: true,
+        canWrite: true,
+      },
+      children: {
+        default: {
+          entry: {
+            isDirectory: true,
+            owners: ["ROLE_CS_ROOT"],
+            readers: ["ROLE_USER"],
+            timestamp: 1607879735685,
+            lastEditor: "admin",
+            canRead: true,
+            canWrite: true,
+          },
+          children: {
+            preferences: {
+              entry: {
+                content: '{\n  "allow": [],\n  "deny": [],\n  "map": {}\n}',
+                isDirectory: false,
+                owners: ["ROLE_CS_ROOT"],
+                readers: ["ROLE_USER"],
+                timestamp: 1607879735685,
+                lastEditor: "admin",
+                canRead: true,
+                canWrite: true,
+              },
+            },
+          },
+        },
+        roles: {
+          entry: {
+            isDirectory: true,
+            owners: ["ROLE_CS_ROOT"],
+            readers: ["ROLE_USER"],
+            timestamp: 1607879735685,
+            lastEditor: "admin",
+            canRead: true,
+            canWrite: true,
+          },
+        },
+        users: {
+          entry: {
+            isDirectory: true,
+            owners: ["ROLE_USER"],
+            readers: ["ROLE_USER"],
+            timestamp: 1607879735685,
+            lastEditor: "admin",
+            canRead: true,
+            canWrite: true,
+          },
+          children: {
+            user1: {
+              entry: {
+                isDirectory: true,
+                owners: ["user1"],
+                readers: ["user1"],
+                timestamp: 1607879735685,
+                lastEditor: "admin",
+                canRead: true,
+                canWrite: true,
+              },
+              children: {
+                preferences: {
+                  entry: {
+                    content:
+                      '{\n  "map": {\n    "defaultPermissions": {\n      "owners": [\n        "user2"\n      ],\n      "readers": [\n        "user2"\n      ]\n    }\n  }\n}',
+                    isDirectory: false,
+                    owners: ["user1"],
+                    readers: ["user1"],
+                    timestamp: 1607879735685,
+                    lastEditor: "admin",
+                    canRead: true,
+                    canWrite: true,
+                  },
+                },
+              },
+            },
+            admin: {
+              entry: {
+                isDirectory: true,
+                owners: ["admin"],
+                readers: ["admin"],
+                timestamp: 1607879735685,
+                lastEditor: "admin",
+                canRead: true,
+                canWrite: true,
+              },
+              children: {
+                preferences: {
+                  entry: {
+                    content:
+                      '{\n  "map": {\n    "tree.search.maxResults": 10,\n    "global.theme": "dark-activeviam",\n    "userFilters.enabled": true,\n    "showLegacyCharts": true,\n    "showLegacyMaps": true,\n    "widgets.Tabular.drillthrough.selectedColumns": {\n      "https://activepivot-ranch.activeviam.com:5900": {\n        "EquityDerivativesCube": [\n          {\n            "functionName": "MemberValue",\n            "columnName": "delta"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "delta"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "gamma"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "gamma"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "pnlVega"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "pnlVega"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "Desk"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "Desk"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "Currency"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "Currency"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "Date"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "Date"\n          },\n          {\n            "columnName": "HostName",\n            "functionName": "MemberValue"\n          },\n          {\n            "columnName": "HostName",\n            "functionName": "Caption"\n          }\n        ],\n        "EquityDerivativesCubeDist": [\n          {\n            "functionName": "MemberValue",\n            "columnName": "BumpedMtmDown"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "BumpedMtmDown"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "vega"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "vega"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "rho"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "rho"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "productId"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "productId"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "pnlVega"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "pnlVega"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "pnlDelta"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "pnlDelta"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "pnl"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "pnl"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "gamma"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "gamma"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "delta"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "delta"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "TradeId"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "TradeId"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductBaseMtm"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductBaseMtm"\n          },\n          {\n            "columnName": "ProductQtyMultiplier",\n            "functionName": "MemberValue"\n          },\n          {\n            "columnName": "ProductQtyMultiplier",\n            "functionName": "Caption"\n          }\n        ]\n      }\n    },\n    "defaultPermissions": {\n      "owners": [\n        "admin"\n      ],\n      "readers": [\n        "admin"\n      ]\n    },\n    "project.content-editor.configuration": {\n      "autoSwitchToFieldsOnEmptyWidget": true,\n      "advancedModeDropdownHidden": false,\n      "hideFieldsControls": false,\n      "mdx-common": {\n        "regularModeTab": "filters",\n        "advancedModeEnabled": false,\n        "advancedModeTab": "mdx"\n      }\n    },\n    "user.contextValues": {\n      "EquityDerivativesCube": {},\n      "EquityDerivativesCubeDist": {}\n    },\n    "user.filters": {\n      "EquityDerivativesCube": ["[Geography].[City].[ALL].[AllMember].[Berlin]"],\n      "EquityDerivativesCubeDist": []\n    },\n    "filtering.hierarchyToFilterType.[Geography].[City]": "explicit",\n    "filtering.hierarchyToFilterType.[Currency].[Currency]": "explicit",\n    "filtering.hierarchyToFilterType.[Trades].[Trades]": "topcount",\n    "servers.alias": {\n      "https://activepivot-ranch.activeviam.com:5900": "http://localhost:8080"\n    }\n  }\n}',
+                    isDirectory: false,
+                    owners: ["admin"],
+                    readers: ["admin"],
+                    timestamp: 1607879735685,
+                    lastEditor: "admin",
+                    canRead: true,
+                    canWrite: true,
+                  },
+                },
+              },
+            },
+          },
+        },
+      },
+    },
+    version: {
+      entry: {
+        content: '{"package":"4.3.8","contentServerApi":"0.1.0"}',
+        isDirectory: false,
+        owners: ["ROLE_CS_ROOT"],
+        readers: ["ROLE_USER"],
+        timestamp: 1607879735685,
+        lastEditor: "admin",
+        canRead: true,
+        canWrite: true,
+      },
+    },
+  },
+};
diff --git a/src/4.3_to_5.0/__test_resources__/invalidLegacyWidgets.ts b/src/4.3_to_5.0/__test_resources__/invalidLegacyWidgets.ts
new file mode 100644
index 0000000..4bf8dc8
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/invalidLegacyWidgets.ts
@@ -0,0 +1,37 @@
+const widgetWithInvalidContainerKey = {
+  entry: {
+    content:
+      '{"description":"Widget with invalid container key","name":"Invalid widget","type":"container","value":{"style":{},"showTitleBar":false,"containerKey":"invalid-container-key","body":{"serverUrl":"","mdx":"SELECT NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [EquityDerivativesCube] WHERE [Geography].[City].[ALL].[AllMember].[New York] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues":{},"updateMode":"once","ranges":{}}}}',
+    isDirectory: false,
+    owners: ["admin"],
+    readers: ["admin"],
+    timestamp: 1607879735685,
+    lastEditor: "admin",
+    canRead: true,
+    canWrite: true,
+  },
+};
+
+const widgetWithFilterOnInvalidHierarchy = {
+  entry: {
+    content:
+      '{"description":"Widget with filter on invalid hierarchy","name":"Invalid widget","type":"container","value":{"style":{},"showTitleBar":false,"containerKey":"pivot-table","body":{"serverUrl":"","mdx":"SELECT NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [EquityDerivativesCube] WHERE [Geography].[InvalidHierarchy].[ALL].[AllMember].[Member] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues":{},"updateMode":"once","ranges":{}}}}',
+    isDirectory: false,
+    owners: ["admin"],
+    readers: ["admin"],
+    timestamp: 1607879735685,
+    lastEditor: "admin",
+    canRead: true,
+    canWrite: true,
+  },
+};
+
+/**
+ * Contains two legacy bookmark widgets.
+ * 1. Widget with an invalid container container key.
+ * 2. Widget with a filter on an invalid hierarchy.
+ */
+export const invalidLegacyWidgets = {
+  "158": widgetWithInvalidContainerKey,
+  "1231": widgetWithFilterOnInvalidHierarchy,
+};
diff --git a/src/4.3_to_5.0/__test_resources__/legacyDashboardBookmark.ts b/src/4.3_to_5.0/__test_resources__/legacyDashboardBookmark.ts
new file mode 100644
index 0000000..03d601d
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/legacyDashboardBookmark.ts
@@ -0,0 +1,16 @@
+/**
+ * Content entry representing a legacy dashboard containing a single pivot table.
+ * Useful for unit tests.
+ */
+export const legacyDashboardBookmark = {
+  entry: {
+    content: `{"name":"hidden grand totals","type":"container","value":{"style":{},"showTitleBar":false,"body":{"pages":[{"content":[{"key":"1","bookmark":{"name":"Untitled Pivot Table","type":"container","value":{"style":{},"showTitleBar":true,"body":{"serverUrl":"","mdx":"SELECT NON EMPTY Crossjoin(Hierarchize(DrilldownLevel([Geography].[City].[ALL].[AllMember])), Hierarchize(DrilldownLevel([Currency].[Currency].[ALL].[AllMember]))) ON ROWS, NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [EquityDerivativesCube] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues":{"mdx.hiddengrandtotals":"1"},"updateMode":"once","ranges":{"row":{"chunkSize":2000,"thresholdPercentage":0.1},"column":{"chunkSize":50,"thresholdPercentage":0.2}},"configuration":{"tabular":{"pinnedHeaderSelector":"member","sortingMode":"non-breaking","addButtonFilter":"numeric","cellRenderers":["tree-layout"],"statisticsShown":true,"columnsGroups":[{"captionProducer":"firstColumn","cellFactory":"kpi-status","selector":"kpi-status"},{"captionProducer":"firstColumn","cellFactory":"lookup","selector":"lookup"},{"captionProducer":"expiry","cellFactory":"expiry","selector":"kpi-expiry"},{"captionProducer":"columnMerge","cellFactory":{"args":{},"key":"treeCells"},"selector":"member"}],"hideAddButton":true,"defaultOptions":{},"expansion":{"automaticExpansion":true}}}},"containerKey":"pivot-table"},"writable":true}},{"key":"2","bookmark":{"name":"Untitled Chart","type":"container","value":{"style":{},"showTitleBar":true,"body":{"configuration":{"type":"plotly-line-chart","mapping":{"xAxis":["[Currency].[Currency].[Currency]"],"values":["[Measures].[pnl.FOREX]"],"splitBy":["[Booking].[Desk].[LegalEntity]"],"horizontalSubplots":[],"verticalSubplots":[]},"switchedTo":"plotly-clustered-column-chart"},"query":{"serverUrl":"","mdx":"SELECT NON EMPTY Crossjoin(Hierarchize(DrilldownLevel([Currency].[Currency])), Hierarchize(DrilldownLevel([Booking].[Desk].[ALL].[AllMember]))) ON ROWS, NON EMPTY [Measures].[pnl.FOREX] ON COLUMNS FROM [EquityDerivativesCube]","contextValues":{},"updateMode":"once"}},"containerKey":"chart"},"writable":true}}],"layout":{"children":{"0":{"ck":"2"},"1":{"ck":"1"}},"direction":"row"},"name":"Page 1","filters":{"EquityDerivativesCube":[]}}]},"containerKey":"dashboard"}}`,
+    isDirectory: false,
+    owners: ["admin"],
+    readers: ["admin"],
+    timestamp: 1607879735685,
+    lastEditor: "admin",
+    canRead: true,
+    canWrite: true,
+  },
+};
diff --git a/src/4.3_to_5.0/__test_resources__/legacyInvalidDashboardBookmark.ts b/src/4.3_to_5.0/__test_resources__/legacyInvalidDashboardBookmark.ts
new file mode 100644
index 0000000..c7f1a92
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/legacyInvalidDashboardBookmark.ts
@@ -0,0 +1,17 @@
+/**
+ * The content entry representing a bookmark of an invalid dashboard.
+ * Useful for unit tests.
+ */
+export const legacyInvalidDashboardBookmark = {
+  entry: {
+    content:
+      '{"name":"hidden grand totals","type":"container","value":{"style":{},"showTitleBar":false,"body":{"pages":[{"content":[{"key":"1","bookmark":{"name":"Untitled Pivot Table","type":"container","value":{"style":{},"showTitleBar":true,"body":{"serverUrl":"","mdx":"SELECT NON EMPTY Crossjoin(Hierarchize(DrilldownLevel([Geography].[City].[ALL].[AllMember])), Hierarchize(DrilldownLevel([Currency].[Currency].[ALL].[AllMember]))) ON ROWS, NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [foo] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues":{"mdx.hiddengrandtotals":"1"},"updateMode":"once","ranges":{"row":{"chunkSize":2000,"thresholdPercentage":0.1},"column":{"chunkSize":50,"thresholdPercentage":0.2}},"configuration":{"tabular":{"pinnedHeaderSelector":"member","sortingMode":"non-breaking","addButtonFilter":"numeric","cellRenderers":["tree-layout"],"statisticsShown":true,"columnsGroups":[{"captionProducer":"firstColumn","cellFactory":"kpi-status","selector":"kpi-status"},{"captionProducer":"firstColumn","cellFactory":"lookup","selector":"lookup"},{"captionProducer":"expiry","cellFactory":"expiry","selector":"kpi-expiry"},{"captionProducer":"columnMerge","cellFactory":{"args":{},"key":"treeCells"},"selector":"member"}],"hideAddButton":true,"defaultOptions":{},"expansion":{"automaticExpansion":true}}}},"containerKey":"pivot-table"},"writable":true}},{"key":"2","bookmark":{"name":"Untitled Chart","type":"container","value":{"style":{},"showTitleBar":true,"body":{"configuration":{"type":"plotly-line-chart","mapping":{"xAxis":["[Currency].[Currency].[Currency]"],"values":["[Measures].[pnl.FOREX]"],"splitBy":["[Booking].[Desk].[LegalEntity]"],"horizontalSubplots":[],"verticalSubplots":[]},"switchedTo":"plotly-clustered-column-chart"},"query":{"serverUrl":"","mdx":"SELECT NON EMPTY Crossjoin(Hierarchize(DrilldownLevel([Currency].[Currency])), Hierarchize(DrilldownLevel([Booking].[Desk].[ALL].[AllMember]))) ON ROWS, NON EMPTY [Measures].[pnl.FOREX] ON COLUMNS FROM [EquityDerivativesCube]","contextValues":{},"updateMode":"once"}},"containerKey":"chart"},"writable":true}}],"layout":{"children":{"0":{"ck":"2"},"1":{"ck":"1"}},"direction":"row"},"name":"Page 1","filters":{"EquityDerivativesCube":[]}}]},"containerKey":"dashboard"}}',
+    isDirectory: false,
+    owners: ["admin"],
+    readers: ["admin"],
+    timestamp: 1607879735685,
+    lastEditor: "admin",
+    canRead: true,
+    canWrite: true,
+  },
+};
diff --git a/src/4.3_to_5.0/__test_resources__/legacyInvalidFilterBookmark.ts b/src/4.3_to_5.0/__test_resources__/legacyInvalidFilterBookmark.ts
new file mode 100644
index 0000000..adbd6c7
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/legacyInvalidFilterBookmark.ts
@@ -0,0 +1,17 @@
+/**
+ * The content entry representing a legacy filter containing an invalid property.
+ * Useful for unit tests.
+ */
+export const legacyInvalidFilterBookmark = {
+  entry: {
+    content:
+      '{"name":"AUI4 filter","type":"mdx","invalidvalue":{"shouldReplace":true,"type":"filter","mdx":"{[Geography].[City].[ALL].[AllMember].[Berlin], [Geography].[City].[ALL].[AllMember].[London]}","cube":"EquityDerivativesCube"}}',
+    isDirectory: false,
+    owners: ["admin"],
+    readers: ["admin"],
+    timestamp: 1607879735685,
+    lastEditor: "admin",
+    canRead: true,
+    canWrite: true,
+  },
+};
diff --git a/src/4.3_to_5.0/__test_resources__/legacyKpiWithInvalidTitle.ts b/src/4.3_to_5.0/__test_resources__/legacyKpiWithInvalidTitle.ts
new file mode 100644
index 0000000..56a7eca
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/legacyKpiWithInvalidTitle.ts
@@ -0,0 +1,18 @@
+/**
+ * The content entry for a legacy bookmark representing a KPI widget.
+ * Useful for unit tests.
+ 
+ */
+export const legacyKpiWithInvalidTitle = {
+  entry: {
+    content:
+      '{"description": "A KPI containing a custom title with an empty tupleKey","name":"KPI","type":"container","value": {"style": {},"showTitleBar": true,"body": {"serverUrl": "","mdx": "SELECT NON EMPTY Hierarchize(AddCalculatedMembers(Descendants({[Geography].[City].[ALL].[AllMember]},1,SELF_AND_BEFORE))) ON ROWS,NON EMPTY {[Measures].[contributors.COUNT]} ON COLUMNS FROM (SELECT[Geography].[City].[ALL].[AllMember].[New York] ON COLUMNS FROM [EquityDerivativesCube])","contextValues": {},"updateMode": "once","ranges": {"row": {},"column": {}},"configuration": {"featuredValues": {"locations":{"":{"title": "Title with empty tupleKey"},"[Measures].[contributors.COUNT]": {"title": "Custom title for contributors.COUNT"}}}}},"containerKey":"featured-values"},"writable": true}',
+    isDirectory: false,
+    owners: ["admin"],
+    readers: ["admin"],
+    timestamp: 1607879735685,
+    lastEditor: "admin",
+    canRead: true,
+    canWrite: true,
+  },
+};
diff --git a/src/4.3_to_5.0/__test_resources__/legacyPivotTableBookmark.ts b/src/4.3_to_5.0/__test_resources__/legacyPivotTableBookmark.ts
new file mode 100644
index 0000000..6c3f3a7
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/legacyPivotTableBookmark.ts
@@ -0,0 +1,16 @@
+/**
+ * The content entry for a legacy bookmark representing a pivot table.
+ */
+export const legacyPivotTableBookmark = {
+  entry: {
+    content:
+      '{"description": "Valid widget","name": "Valid widget","type": "container", "value": {"style": {},"showTitleBar": false,"containerKey": "pivot-table","body": {"serverUrl": "","mdx": "SELECT NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [EquityDerivativesCube] WHERE [Geography].[City].[ALL].[AllMember].[New York] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues": {},"updateMode": "once", "ranges": {}}}}',
+    isDirectory: false,
+    owners: ["admin"],
+    readers: ["admin"],
+    timestamp: 1607879735685,
+    lastEditor: "admin",
+    canRead: true,
+    canWrite: true,
+  },
+};
diff --git a/src/4.3_to_5.0/__test_resources__/legacyUIFolderWithInvalidKpi.ts b/src/4.3_to_5.0/__test_resources__/legacyUIFolderWithInvalidKpi.ts
new file mode 100644
index 0000000..ad5a89f
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/legacyUIFolderWithInvalidKpi.ts
@@ -0,0 +1,14 @@
+import { addLegacyBookmarkToUIFolder } from "./addLegacyBookmarkToUIFolder";
+import { emptyLegacyUIFolder } from "./emptyLegacyUIFolder";
+import { legacyKpiWithInvalidTitle } from "./legacyKpiWithInvalidTitle";
+
+/**
+ * A legacy UI folder containing a single KPI bookmark with an invalid KPI title.
+ * Useful for unit tests.
+ */
+export const legacyUIFolderWithInvalidKpiTitle = addLegacyBookmarkToUIFolder(
+  emptyLegacyUIFolder,
+  {
+    kpi: legacyKpiWithInvalidTitle,
+  },
+);
diff --git a/src/4.3_to_5.0/__test_resources__/legacyUIFolderWithInvalidWidgets.ts b/src/4.3_to_5.0/__test_resources__/legacyUIFolderWithInvalidWidgets.ts
new file mode 100644
index 0000000..17e4548
--- /dev/null
+++ b/src/4.3_to_5.0/__test_resources__/legacyUIFolderWithInvalidWidgets.ts
@@ -0,0 +1,15 @@
+import { addLegacyBookmarkToUIFolder } from "./addLegacyBookmarkToUIFolder";
+import { emptyLegacyUIFolder } from "./emptyLegacyUIFolder";
+import { invalidLegacyWidgets } from "./invalidLegacyWidgets";
+import { legacyPivotTableBookmark } from "./legacyPivotTableBookmark";
+
+/**
+ * Contains three legacy bookmark widgets.
+ * 1. Widget with an invalid container container key.
+ * 2. Widget with a filter on an invalid hierarchy.
+ * 3. A valid widget.
+ */
+export const legacyUIFolderWithInvalidWidgets = addLegacyBookmarkToUIFolder(
+  emptyLegacyUIFolder,
+  { ...invalidLegacyWidgets, "777": legacyPivotTableBookmark },
+);
diff --git a/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolder.ts b/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolder.ts
index aeb3ad7..e00cc38 100644
--- a/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolder.ts
+++ b/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolder.ts
@@ -1,240 +1,11 @@
+import { addLegacyBookmarkToUIFolder } from "./addLegacyBookmarkToUIFolder";
+import { emptyLegacyUIFolder } from "./emptyLegacyUIFolder";
+import { legacyDashboardBookmark } from "./legacyDashboardBookmark";
+
 /**
  * The shortened version of the content of the /ui folder on a Content Server, useful for unit tests.
  */
-export const smallLegacyUIFolder = {
-  entry: {
-    isDirectory: true,
-    owners: ["admin"],
-    readers: ["admin"],
-    timestamp: 1607879725132,
-    lastEditor: "admin",
-    canRead: true,
-    canWrite: true,
-  },
-  children: {
-    bookmarks: {
-      entry: {
-        isDirectory: true,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-      children: {
-        content: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_USER"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "158": {
-              entry: {
-                content:
-                  '{"name":"hidden grand totals","type":"container","value":{"style":{},"showTitleBar":false,"body":{"pages":[{"content":[{"key":"1","bookmark":{"name":"Untitled Pivot Table","type":"container","value":{"style":{},"showTitleBar":true,"body":{"serverUrl":"","mdx":"SELECT NON EMPTY Crossjoin(Hierarchize(DrilldownLevel([Geography].[City].[ALL].[AllMember])), Hierarchize(DrilldownLevel([Currency].[Currency].[ALL].[AllMember]))) ON ROWS, NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [EquityDerivativesCube] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues":{"mdx.hiddengrandtotals":"1"},"updateMode":"once","ranges":{"row":{"chunkSize":2000,"thresholdPercentage":0.1},"column":{"chunkSize":50,"thresholdPercentage":0.2}},"configuration":{"tabular":{"pinnedHeaderSelector":"member","sortingMode":"non-breaking","addButtonFilter":"numeric","cellRenderers":["tree-layout"],"statisticsShown":true,"columnsGroups":[{"captionProducer":"firstColumn","cellFactory":"kpi-status","selector":"kpi-status"},{"captionProducer":"firstColumn","cellFactory":"lookup","selector":"lookup"},{"captionProducer":"expiry","cellFactory":"expiry","selector":"kpi-expiry"},{"captionProducer":"columnMerge","cellFactory":{"args":{},"key":"treeCells"},"selector":"member"}],"hideAddButton":true,"defaultOptions":{},"expansion":{"automaticExpansion":true}}}},"containerKey":"pivot-table"},"writable":true}},{"key":"2","bookmark":{"name":"Untitled Chart","type":"container","value":{"style":{},"showTitleBar":true,"body":{"configuration":{"type":"plotly-line-chart","mapping":{"xAxis":["[Currency].[Currency].[Currency]"],"values":["[Measures].[pnl.FOREX]"],"splitBy":["[Booking].[Desk].[LegalEntity]"],"horizontalSubplots":[],"verticalSubplots":[]},"switchedTo":"plotly-clustered-column-chart"},"query":{"serverUrl":"","mdx":"SELECT NON EMPTY Crossjoin(Hierarchize(DrilldownLevel([Currency].[Currency])), Hierarchize(DrilldownLevel([Booking].[Desk].[ALL].[AllMember]))) ON ROWS, NON EMPTY [Measures].[pnl.FOREX] ON COLUMNS FROM [EquityDerivativesCube]","contextValues":{},"updateMode":"once"}},"containerKey":"chart"},"writable":true}}],"layout":{"children":{"0":{"ck":"2"},"1":{"ck":"1"}},"direction":"row"},"name":"Page 1","filters":{"EquityDerivativesCube":[]}}]},"containerKey":"dashboard"}}',
-                isDirectory: false,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-        i18n: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_CS_ROOT"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "en-US": {
-              entry: {
-                isDirectory: true,
-                owners: ["ROLE_CS_ROOT"],
-                readers: ["ROLE_USER"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-            "fr-FR": {
-              entry: {
-                isDirectory: true,
-                owners: ["ROLE_CS_ROOT"],
-                readers: ["ROLE_USER"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-        structure: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_USER"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "158": {
-              entry: {
-                isDirectory: true,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-      },
-    },
-    settings: {
-      entry: {
-        isDirectory: true,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-      children: {
-        default: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_CS_ROOT"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            preferences: {
-              entry: {
-                content: '{\n  "allow": [],\n  "deny": [],\n  "map": {}\n}',
-                isDirectory: false,
-                owners: ["ROLE_CS_ROOT"],
-                readers: ["ROLE_USER"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-        roles: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_CS_ROOT"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-        },
-        users: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_USER"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            user1: {
-              entry: {
-                isDirectory: true,
-                owners: ["user1"],
-                readers: ["user1"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-              children: {
-                preferences: {
-                  entry: {
-                    content:
-                      '{\n  "map": {\n    "defaultPermissions": {\n      "owners": [\n        "user2"\n      ],\n      "readers": [\n        "user2"\n      ]\n    }\n  }\n}',
-                    isDirectory: false,
-                    owners: ["user1"],
-                    readers: ["user1"],
-                    timestamp: 1607879735685,
-                    lastEditor: "admin",
-                    canRead: true,
-                    canWrite: true,
-                  },
-                },
-              },
-            },
-            admin: {
-              entry: {
-                isDirectory: true,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-              children: {
-                preferences: {
-                  entry: {
-                    content:
-                      '{\n  "map": {\n    "tree.search.maxResults": 10,\n    "global.theme": "dark-activeviam",\n    "userFilters.enabled": true,\n    "showLegacyCharts": true,\n    "showLegacyMaps": true,\n    "widgets.Tabular.drillthrough.selectedColumns": {\n      "https://activepivot-ranch.activeviam.com:5900": {\n        "EquityDerivativesCube": [\n          {\n            "functionName": "MemberValue",\n            "columnName": "delta"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "delta"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "gamma"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "gamma"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "pnlVega"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "pnlVega"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "Desk"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "Desk"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "Currency"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "Currency"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "Date"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "Date"\n          },\n          {\n            "columnName": "HostName",\n            "functionName": "MemberValue"\n          },\n          {\n            "columnName": "HostName",\n            "functionName": "Caption"\n          }\n        ],\n        "EquityDerivativesCubeDist": [\n          {\n            "functionName": "MemberValue",\n            "columnName": "BumpedMtmDown"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "BumpedMtmDown"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "vega"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "vega"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "rho"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "rho"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "productId"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "productId"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "pnlVega"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "pnlVega"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "pnlDelta"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "pnlDelta"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "pnl"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "pnl"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "gamma"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "gamma"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "delta"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "delta"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "TradeId"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "TradeId"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductQtyMultiplier"\n          },\n          {\n            "functionName": "MemberValue",\n            "columnName": "ProductBaseMtm"\n          },\n          {\n            "functionName": "Caption",\n            "columnName": "ProductBaseMtm"\n          },\n          {\n            "columnName": "ProductQtyMultiplier",\n            "functionName": "MemberValue"\n          },\n          {\n            "columnName": "ProductQtyMultiplier",\n            "functionName": "Caption"\n          }\n        ]\n      }\n    },\n    "defaultPermissions": {\n      "owners": [\n        "admin"\n      ],\n      "readers": [\n        "admin"\n      ]\n    },\n    "project.content-editor.configuration": {\n      "autoSwitchToFieldsOnEmptyWidget": true,\n      "advancedModeDropdownHidden": false,\n      "hideFieldsControls": false,\n      "mdx-common": {\n        "regularModeTab": "filters",\n        "advancedModeEnabled": false,\n        "advancedModeTab": "mdx"\n      }\n    },\n    "user.contextValues": {\n      "EquityDerivativesCube": {},\n      "EquityDerivativesCubeDist": {}\n    },\n    "user.filters": {\n      "EquityDerivativesCube": ["[Geography].[City].[ALL].[AllMember].[Berlin]"],\n      "EquityDerivativesCubeDist": []\n    },\n    "filtering.hierarchyToFilterType.[Geography].[City]": "explicit",\n    "filtering.hierarchyToFilterType.[Currency].[Currency]": "explicit",\n    "filtering.hierarchyToFilterType.[Trades].[Trades]": "topcount",\n    "servers.alias": {\n      "https://activepivot-ranch.activeviam.com:5900": "http://localhost:8080"\n    }\n  }\n}',
-                    isDirectory: false,
-                    owners: ["admin"],
-                    readers: ["admin"],
-                    timestamp: 1607879735685,
-                    lastEditor: "admin",
-                    canRead: true,
-                    canWrite: true,
-                  },
-                },
-              },
-            },
-          },
-        },
-      },
-    },
-    version: {
-      entry: {
-        content: '{"package":"4.3.8","contentServerApi":"0.1.0"}',
-        isDirectory: false,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-    },
-  },
-};
+export const smallLegacyUIFolder = addLegacyBookmarkToUIFolder(
+  emptyLegacyUIFolder,
+  { "158": legacyDashboardBookmark },
+);
diff --git a/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidDashboard.ts b/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidDashboard.ts
index 713fbb9..e06eacf 100644
--- a/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidDashboard.ts
+++ b/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidDashboard.ts
@@ -1,138 +1,12 @@
+import { addLegacyBookmarkToUIFolder } from "./addLegacyBookmarkToUIFolder";
+import { emptyLegacyUIFolder } from "./emptyLegacyUIFolder";
+import { legacyInvalidDashboardBookmark } from "./legacyInvalidDashboardBookmark";
+
 /**
  * The shortened version of the content of the /ui folder on a Content Server, useful for unit tests.
  * Contains an invalid dashboard whose id is numerical.
  */
-export const smallLegacyUIFolderWithInvalidDashboard = {
-  entry: {
-    isDirectory: true,
-    owners: ["admin"],
-    readers: ["admin"],
-    timestamp: 1607879725132,
-    lastEditor: "admin",
-    canRead: true,
-    canWrite: true,
-  },
-  children: {
-    bookmarks: {
-      entry: {
-        isDirectory: true,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-      children: {
-        content: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_USER"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "158": {
-              entry: {
-                content:
-                  '{"name":"hidden grand totals","type":"container","value":{"style":{},"showTitleBar":false,"body":{"pages":[{"content":[{"key":"1","bookmark":{"name":"Untitled Pivot Table","type":"container","value":{"style":{},"showTitleBar":true,"body":{"serverUrl":"","mdx":"SELECT NON EMPTY Crossjoin(Hierarchize(DrilldownLevel([Geography].[City].[ALL].[AllMember])), Hierarchize(DrilldownLevel([Currency].[Currency].[ALL].[AllMember]))) ON ROWS, NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [foo] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues":{"mdx.hiddengrandtotals":"1"},"updateMode":"once","ranges":{"row":{"chunkSize":2000,"thresholdPercentage":0.1},"column":{"chunkSize":50,"thresholdPercentage":0.2}},"configuration":{"tabular":{"pinnedHeaderSelector":"member","sortingMode":"non-breaking","addButtonFilter":"numeric","cellRenderers":["tree-layout"],"statisticsShown":true,"columnsGroups":[{"captionProducer":"firstColumn","cellFactory":"kpi-status","selector":"kpi-status"},{"captionProducer":"firstColumn","cellFactory":"lookup","selector":"lookup"},{"captionProducer":"expiry","cellFactory":"expiry","selector":"kpi-expiry"},{"captionProducer":"columnMerge","cellFactory":{"args":{},"key":"treeCells"},"selector":"member"}],"hideAddButton":true,"defaultOptions":{},"expansion":{"automaticExpansion":true}}}},"containerKey":"pivot-table"},"writable":true}},{"key":"2","bookmark":{"name":"Untitled Chart","type":"container","value":{"style":{},"showTitleBar":true,"body":{"configuration":{"type":"plotly-line-chart","mapping":{"xAxis":["[Currency].[Currency].[Currency]"],"values":["[Measures].[pnl.FOREX]"],"splitBy":["[Booking].[Desk].[LegalEntity]"],"horizontalSubplots":[],"verticalSubplots":[]},"switchedTo":"plotly-clustered-column-chart"},"query":{"serverUrl":"","mdx":"SELECT NON EMPTY Crossjoin(Hierarchize(DrilldownLevel([Currency].[Currency])), Hierarchize(DrilldownLevel([Booking].[Desk].[ALL].[AllMember]))) ON ROWS, NON EMPTY [Measures].[pnl.FOREX] ON COLUMNS FROM [EquityDerivativesCube]","contextValues":{},"updateMode":"once"}},"containerKey":"chart"},"writable":true}}],"layout":{"children":{"0":{"ck":"2"},"1":{"ck":"1"}},"direction":"row"},"name":"Page 1","filters":{"EquityDerivativesCube":[]}}]},"containerKey":"dashboard"}}',
-                isDirectory: false,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-        i18n: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_CS_ROOT"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "en-US": {
-              entry: {
-                isDirectory: true,
-                owners: ["ROLE_CS_ROOT"],
-                readers: ["ROLE_USER"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-            "fr-FR": {
-              entry: {
-                isDirectory: true,
-                owners: ["ROLE_CS_ROOT"],
-                readers: ["ROLE_USER"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-        structure: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_USER"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "158": {
-              entry: {
-                isDirectory: true,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-      },
-    },
-    settings: {
-      entry: {
-        isDirectory: true,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-    },
-    version: {
-      entry: {
-        content: '{"package":"4.3.8","contentServerApi":"0.1.0"}',
-        isDirectory: false,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-    },
-  },
-};
+export const smallLegacyUIFolderWithInvalidDashboard =
+  addLegacyBookmarkToUIFolder(emptyLegacyUIFolder, {
+    "158": legacyInvalidDashboardBookmark,
+  });
diff --git a/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidFilter.ts b/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidFilter.ts
index 7fee55e..87fff2c 100644
--- a/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidFilter.ts
+++ b/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidFilter.ts
@@ -1,139 +1,12 @@
+import { addLegacyBookmarkToUIFolder } from "./addLegacyBookmarkToUIFolder";
+import { emptyLegacyUIFolder } from "./emptyLegacyUIFolder";
+import { legacyInvalidFilterBookmark } from "./legacyInvalidFilterBookmark";
+
 /**
  * The shortened version of the content of the /ui folder on a Content Server, useful for unit tests.
  * Contains an invalid filter.
  */
-export const smallLegacyUIFolderWithInvalidFilter = {
-  entry: {
-    isDirectory: true,
-    owners: ["admin"],
-    readers: ["admin"],
-    timestamp: 1607879725132,
-    lastEditor: "admin",
-    canRead: true,
-    canWrite: true,
-  },
-  children: {
-    bookmarks: {
-      entry: {
-        isDirectory: true,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-      children: {
-        content: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_USER"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "158": {
-              entry: {
-                content:
-                  '{"name":"AUI4 filter","type":"mdx","invalidvalue":{"shouldReplace":true,"type":"filter","mdx":"{[Geography].[City].[ALL].[AllMember].[Berlin], [Geography].[City].[ALL].[AllMember].[London]}","cube":"EquityDerivativesCube"}}',
-                isDirectory: false,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-        i18n: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_CS_ROOT"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "en-US": {
-              entry: {
-                isDirectory: true,
-                owners: ["ROLE_CS_ROOT"],
-                readers: ["ROLE_USER"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-            "fr-FR": {
-              entry: {
-                isDirectory: true,
-                owners: ["ROLE_CS_ROOT"],
-                readers: ["ROLE_USER"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-        structure: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_USER"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "158": {
-              entry: {
-                isDirectory: true,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-      },
-    },
-    settings: {
-      entry: {
-        isDirectory: true,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-      children: {},
-    },
-    version: {
-      entry: {
-        content: '{"package":"4.3.8","contentServerApi":"0.1.0"}',
-        isDirectory: false,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-    },
-  },
-};
+export const smallLegacyUIFolderWithInvalidFilter = addLegacyBookmarkToUIFolder(
+  emptyLegacyUIFolder,
+  { "158": legacyInvalidFilterBookmark },
+);
diff --git a/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidWidget.ts b/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidWidget.ts
deleted file mode 100644
index 33948e4..0000000
--- a/src/4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidWidget.ts
+++ /dev/null
@@ -1,186 +0,0 @@
-/**
- * The shortened version of the content of the /ui folder on a Content Server, useful for unit tests.
- * Contains a valid widget, a widget whose `containerKey` is not valid, and another widget with a filter on a hierarchy that does not exist in the test cube.
- */
-export const smallLegacyUIFolderWithInvalidWidget = {
-  entry: {
-    isDirectory: true,
-    owners: ["admin"],
-    readers: ["admin"],
-    timestamp: 1607879725132,
-    lastEditor: "admin",
-    canRead: true,
-    canWrite: true,
-  },
-  children: {
-    bookmarks: {
-      entry: {
-        isDirectory: true,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-      children: {
-        content: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_USER"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "158": {
-              entry: {
-                content:
-                  '{"description":"Widget with invalid container key","name":"Invalid widget","type":"container","value":{"style":{},"showTitleBar":false,"containerKey":"invalid-container-key","body":{"serverUrl":"","mdx":"SELECT NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [EquityDerivativesCube] WHERE [Geography].[City].[ALL].[AllMember].[New York] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues":{},"updateMode":"once","ranges":{}}}}',
-                isDirectory: false,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-            "1231": {
-              entry: {
-                content:
-                  '{"description":"Widget with filter on invalid hierarchy","name":"Invalid widget","type":"container","value":{"style":{},"showTitleBar":false,"containerKey":"pivot-table","body":{"serverUrl":"","mdx":"SELECT NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [EquityDerivativesCube] WHERE [Geography].[InvalidHierarchy].[ALL].[AllMember].[Member] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues":{},"updateMode":"once","ranges":{}}}}',
-                isDirectory: false,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-            "777": {
-              entry: {
-                content:
-                  '{"description": "Valid widget","name": "Valid widget","type": "container", "value": {"style": {},"showTitleBar": false,"containerKey": "pivot-table","body": {"serverUrl": "","mdx": "SELECT NON EMPTY [Measures].[contributors.COUNT] ON COLUMNS FROM [EquityDerivativesCube] WHERE [Geography].[City].[ALL].[AllMember].[New York] CELL PROPERTIES VALUE, FORMATTED_VALUE, BACK_COLOR, FORE_COLOR, FONT_FLAGS","contextValues": {},"updateMode": "once", "ranges": {}}}}',
-                isDirectory: false,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-        i18n: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_CS_ROOT"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "en-US": {
-              entry: {
-                isDirectory: true,
-                owners: ["ROLE_CS_ROOT"],
-                readers: ["ROLE_USER"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-            "fr-FR": {
-              entry: {
-                isDirectory: true,
-                owners: ["ROLE_CS_ROOT"],
-                readers: ["ROLE_USER"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-        structure: {
-          entry: {
-            isDirectory: true,
-            owners: ["ROLE_USER"],
-            readers: ["ROLE_USER"],
-            timestamp: 1607879735685,
-            lastEditor: "admin",
-            canRead: true,
-            canWrite: true,
-          },
-          children: {
-            "158": {
-              entry: {
-                isDirectory: true,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-            "1231": {
-              entry: {
-                isDirectory: true,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-            "777": {
-              entry: {
-                isDirectory: true,
-                owners: ["admin"],
-                readers: ["admin"],
-                timestamp: 1607879735685,
-                lastEditor: "admin",
-                canRead: true,
-                canWrite: true,
-              },
-            },
-          },
-        },
-      },
-    },
-    settings: {
-      entry: {
-        isDirectory: true,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-    },
-    version: {
-      entry: {
-        content: '{"package":"4.3.8","contentServerApi":"0.1.0"}',
-        isDirectory: false,
-        owners: ["ROLE_CS_ROOT"],
-        readers: ["ROLE_USER"],
-        timestamp: 1607879735685,
-        lastEditor: "admin",
-        canRead: true,
-        canWrite: true,
-      },
-    },
-  },
-};
diff --git a/src/4.3_to_5.0/getMigratedKpiTitles.test.ts b/src/4.3_to_5.0/accumulateMigratedKpiTitles.test.ts
similarity index 68%
rename from src/4.3_to_5.0/getMigratedKpiTitles.test.ts
rename to src/4.3_to_5.0/accumulateMigratedKpiTitles.test.ts
index f720a44..fee405d 100644
--- a/src/4.3_to_5.0/getMigratedKpiTitles.test.ts
+++ b/src/4.3_to_5.0/accumulateMigratedKpiTitles.test.ts
@@ -1,13 +1,14 @@
 import { dataModelsForTests } from "@activeviam/data-model-5.0";
-import { getMigratedKpiTitles } from "./getMigratedKpiTitles";
+import { accumulateMigratedKpiTitles } from "./accumulateMigratedKpiTitles";
 import { legacyKpi } from "./__test_resources__/legacyKpi";
 import { _getQueryInLegacyWidgetState } from "./_getQueryInLegacyWidgetState";
 import { MdxSelect, parse } from "@activeviam/mdx-5.0";
+import { KpiWidgetState } from "@activeviam/activeui-sdk-5.0";
 
 const cube = dataModelsForTests.sandbox.catalogs[0].cubes[0];
 
-describe("getMigratedKpiTitles", () => {
-  it("returns the migrated KPI titles corresponding to the legacy KPI state, ready to be used in Atoti UI 5.0", () => {
+describe("accumulateMigratedKpiTitles", () => {
+  it("accumulates the migrated KPI titles corresponding to the legacy KPI state, ready to be used in Atoti UI 5.0", () => {
     const legacyQuery = _getQueryInLegacyWidgetState(legacyKpi);
 
     if (!legacyQuery || !legacyQuery.mdx) {
@@ -15,7 +16,9 @@ describe("getMigratedKpiTitles", () => {
     }
 
     const legacyMdx = parse<MdxSelect>(legacyQuery.mdx);
-    const migratedKpiTitles = getMigratedKpiTitles(legacyKpi, {
+    const migratedTitles: KpiWidgetState["titles"] = {};
+    accumulateMigratedKpiTitles(legacyKpi, {
+      migratedTitles,
       cube,
       legacyMdx,
       mapping: {
@@ -31,7 +34,7 @@ describe("getMigratedKpiTitles", () => {
         ],
       },
     });
-    expect(migratedKpiTitles).toMatchInlineSnapshot(`
+    expect(migratedTitles).toMatchInlineSnapshot(`
       {
         "[Measures].[contributors.COUNT],[Currency].[Currency].[AllMember].[EUR, USD]": "Hello World",
       }
diff --git a/src/4.3_to_5.0/getMigratedKpiTitles.ts b/src/4.3_to_5.0/accumulateMigratedKpiTitles.ts
similarity index 54%
rename from src/4.3_to_5.0/getMigratedKpiTitles.ts
rename to src/4.3_to_5.0/accumulateMigratedKpiTitles.ts
index 11b21eb..2abb7ab 100644
--- a/src/4.3_to_5.0/getMigratedKpiTitles.ts
+++ b/src/4.3_to_5.0/accumulateMigratedKpiTitles.ts
@@ -43,24 +43,27 @@ function _getLegacyKpiTitles(
     } = {};
     const memberUniqueNames = tupleKey.split(/,(?![^\[]*\])/);
     for (const memberUniqueName of memberUniqueNames) {
-      const compoundIdentifier =
-        parse<MdxUnknownCompoundIdentifier>(memberUniqueName);
-      const specificCompoundIdentifier = getSpecificCompoundIdentifier(
-        compoundIdentifier,
-        { cube },
-      );
-      if (specificCompoundIdentifier.type === "measure") {
-        tuple[`[Measures].[Measures]`] = [
-          specificCompoundIdentifier.measureName,
-        ];
-      } else if (specificCompoundIdentifier.type === "member") {
-        const hierarchyUniqueName = quote(
-          specificCompoundIdentifier.dimensionName,
-          specificCompoundIdentifier.hierarchyName,
+      if (memberUniqueName) {
+        const compoundIdentifier =
+          parse<MdxUnknownCompoundIdentifier>(memberUniqueName);
+        const specificCompoundIdentifier = getSpecificCompoundIdentifier(
+          compoundIdentifier,
+          { cube },
         );
-        tuple[hierarchyUniqueName] = specificCompoundIdentifier.path;
+        if (specificCompoundIdentifier.type === "measure") {
+          tuple[`[Measures].[Measures]`] = [
+            specificCompoundIdentifier.measureName,
+          ];
+        } else if (specificCompoundIdentifier.type === "member") {
+          const hierarchyUniqueName = quote(
+            specificCompoundIdentifier.dimensionName,
+            specificCompoundIdentifier.hierarchyName,
+          );
+          tuple[hierarchyUniqueName] = specificCompoundIdentifier.path;
+        }
       }
     }
+
     legacyTitles.push({ title, tuple });
   }
 
@@ -68,24 +71,27 @@ function _getLegacyKpiTitles(
 }
 
 /**
- * Returns the migrated KPI widget titles corresponding to legacyKpiState.
+ * Accumulates the migrated KPI widget titles corresponding to legacyKpiState.
+ * Mutates `migratedTitles`.
  */
-export function getMigratedKpiTitles(
+export function accumulateMigratedKpiTitles(
   // Legacy widget states are not typed.
   // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types
   legacyKpiState: any,
   {
+    migratedTitles = {},
     legacyMdx,
     mapping,
     cube,
   }: {
+    migratedTitles: KpiWidgetState["titles"];
     legacyMdx: MdxSelect;
     mapping: DataVisualizationWidgetMapping;
     cube: Cube;
   },
-): KpiWidgetState["titles"] {
+): void {
   const legacyTitles = _getLegacyKpiTitles(legacyKpiState, { cube });
-  const migratedTitles: KpiWidgetState["titles"] = {};
+  const errors: Error[] = [];
 
   const numberOfColumnFields = mapping.columns?.length ?? 0;
 
@@ -107,35 +113,44 @@ export function getMigratedKpiTitles(
   const ordinalFields = [...(mapping.columns ?? []), ...(mapping.rows ?? [])];
 
   legacyTitles.forEach(({ title, tuple }) => {
-    const memberUniqueNames: string[] = [];
+    try {
+      const memberUniqueNames: string[] = [];
 
-    ordinalFields.forEach((field) => {
-      if (field.type === "hierarchy") {
-        const hierarchyUniqueName = quote(
-          field.dimensionName,
-          field.hierarchyName,
-        );
-        const namePath = tuple[hierarchyUniqueName];
-        if (namePath) {
-          memberUniqueNames.push(
-            `${hierarchyUniqueName}.${quote(...namePath)}`,
+      ordinalFields.forEach((field) => {
+        if (field.type === "hierarchy") {
+          const hierarchyUniqueName = quote(
+            field.dimensionName,
+            field.hierarchyName,
           );
+          const namePath = tuple[hierarchyUniqueName];
+          if (namePath) {
+            memberUniqueNames.push(
+              `${hierarchyUniqueName}.${quote(...namePath)}`,
+            );
+          }
         }
+      });
+
+      if (measuresPositionInTuple > -1) {
+        const measureName = tuple[quote("Measures", "Measures")][0];
+        memberUniqueNames.splice(
+          measuresPositionInTuple,
+          0,
+          quote("Measures", measureName),
+        );
       }
-    });
-
-    if (measuresPositionInTuple > -1) {
-      const measureName = tuple[quote("Measures", "Measures")][0];
-      memberUniqueNames.splice(
-        measuresPositionInTuple,
-        0,
-        quote("Measures", measureName),
-      );
-    }
 
-    const tupleKey = memberUniqueNames.join(",");
-    migratedTitles[tupleKey] = title;
+      const tupleKey = memberUniqueNames.join(",");
+      migratedTitles[tupleKey] = title;
+    } catch (error) {
+      errors.push(error as Error);
+    }
   });
 
-  return migratedTitles;
+  if (errors.length > 0) {
+    throw new Error(
+      `One or more errors occurred while migrating the titles for the kpi named ${legacyKpiState.name}: ` +
+        errors.map((e) => e.message).join(", "),
+    );
+  }
 }
diff --git a/src/4.3_to_5.0/migrateKpi.ts b/src/4.3_to_5.0/migrateKpi.ts
index 96c799a..592389d 100644
--- a/src/4.3_to_5.0/migrateKpi.ts
+++ b/src/4.3_to_5.0/migrateKpi.ts
@@ -29,7 +29,7 @@ import { _getQueryInLegacyWidgetState } from "./_getQueryInLegacyWidgetState";
 import { _getTargetCubeFromServerUrl } from "./_getTargetCubeFromServerUrl";
 import { _migrateQuery } from "./_migrateQuery";
 import { produce } from "immer";
-import { getMigratedKpiTitles } from "./getMigratedKpiTitles";
+import { accumulateMigratedKpiTitles } from "./accumulateMigratedKpiTitles";
 import { PartialMigrationError } from "../PartialMigrationError";
 
 const moveExpressionToWithClause = (
@@ -210,13 +210,15 @@ export function migrateKpi(
     }),
   };
 
+  const migratedTitles: KpiWidgetState["titles"] = {};
   try {
     if (legacyMdx) {
       // Migrate manually entered KPI titles.
-      const migratedTitles = getMigratedKpiTitles(legacyKpiState, {
+      accumulateMigratedKpiTitles(legacyKpiState, {
         cube,
         mapping,
         legacyMdx,
+        migratedTitles,
       });
       if (migratedTitles && Object.keys(migratedTitles).length > 0) {
         migratedWidgetState.titles = migratedTitles;
@@ -224,6 +226,11 @@ export function migrateKpi(
     }
   } catch (error) {
     // Migrating the KPI titles is a best effort.
+    // If there is an error while migrating one of the titles, the successfully migrated titles are still persisted.
+    if (migratedTitles && Object.keys(migratedTitles).length > 0) {
+      migratedWidgetState.titles = migratedTitles;
+    }
+
     // The migration script should not fail if this part errors.
     throw new PartialMigrationError(
       `Could not migrate the titles of the featured values widget named "${legacyKpiState.name}"`,
diff --git a/src/migrateContentServer.test.ts b/src/migrateContentServer.test.ts
index bde990b..7ef13d2 100644
--- a/src/migrateContentServer.test.ts
+++ b/src/migrateContentServer.test.ts
@@ -4,7 +4,8 @@ import { smallLegacyPivotFolder } from "./4.3_to_5.0/__test_resources__/smallLeg
 import { smallLegacyUIFolder } from "./4.3_to_5.0/__test_resources__/smallLegacyUIFolder";
 import { migrateContentServer } from "./migrateContentServer";
 import _cloneDeep from "lodash/cloneDeep";
-import { smallLegacyUIFolderWithInvalidWidget } from "./4.3_to_5.0/__test_resources__/smallLegacyUIFolderWithInvalidWidget";
+import { legacyUIFolderWithInvalidWidgets } from "./4.3_to_5.0/__test_resources__/legacyUIFolderWithInvalidWidgets";
+import { legacyUIFolderWithInvalidKpiTitle } from "./4.3_to_5.0/__test_resources__/legacyUIFolderWithInvalidKpi";
 
 jest.mock(`./4.3_to_5.0/generateId`, () => {
   let counter = 0;
@@ -237,7 +238,7 @@ describe("migrateContentServer", () => {
   it("keeps the original item untouched, as before the whole migration when the item cannot be migrated due to an error and the `behaviorOnError` flag is set to `keep-original`.", async () => {
     const contentServer: ContentRecord = {
       children: {
-        ui: smallLegacyUIFolderWithInvalidWidget,
+        ui: legacyUIFolderWithInvalidWidgets,
         pivot: smallLegacyPivotFolder,
       },
       entry: {
@@ -287,7 +288,7 @@ describe("migrateContentServer", () => {
   it("keeps the 5.0 version of the widget, when migrating from 4.3 to 5.1 with `behaviorOnError` set to `keep-last-successful-version` and the 5.0 to 5.1 step fails", async () => {
     const contentServer: ContentRecord = {
       children: {
-        ui: smallLegacyUIFolderWithInvalidWidget,
+        ui: legacyUIFolderWithInvalidWidgets,
         pivot: smallLegacyPivotFolder,
       },
       entry: {
@@ -336,4 +337,68 @@ describe("migrateContentServer", () => {
     // The filters in 5.0 are represented as strings.
     expect(typeof migratedWidgetFilter.mdx).toBe("string");
   });
+
+  it("migrates the KPI custom titles while dropping custom titles that could not be successfully migrated", async () => {
+    const contentServer: ContentRecord = {
+      children: {
+        ui: legacyUIFolderWithInvalidKpiTitle,
+        pivot: smallLegacyPivotFolder,
+      },
+      entry: {
+        owners: [],
+        readers: [],
+        isDirectory: true,
+        canRead: true,
+        canWrite: false,
+        lastEditor: "Freddie Mercury",
+        timestamp: 0xbeef,
+      },
+    };
+
+    const contentServerBeforeMigration = _cloneDeep(contentServer);
+
+    await migrateContentServer({
+      contentServer,
+      servers,
+      fromVersion: "4.3",
+      toVersion: "5.1",
+      keysOfWidgetPluginsToRemove: [],
+      doesReportIncludeStacks: false,
+      shouldUpdateFiltersMdx: true,
+      behaviorOnError: "keep-original",
+    });
+
+    const kpiContentBeforeMigration = JSON.parse(
+      contentServerBeforeMigration.children?.ui.children?.bookmarks.children
+        ?.content.children?.["kpi"].entry.content,
+    );
+
+    expect(
+      kpiContentBeforeMigration.value.body.configuration["featuredValues"]
+        .locations,
+    ).toMatchInlineSnapshot(`
+      {
+        "": {
+          "title": "Title with empty tupleKey",
+        },
+        "[Measures].[contributors.COUNT]": {
+          "title": "Custom title for contributors.COUNT",
+        },
+      }
+    `);
+
+    // The widget with id "kpi" contains a custom title referenced with an empty `tupleKey`.
+    // Because this is not a valid `tupleKey`, the title is dropped.
+    const migratedKpiContent = JSON.parse(
+      contentServer.children?.ui.children?.widgets.children?.content.children?.[
+        "kpi"
+      ].entry.content,
+    );
+
+    expect(migratedKpiContent?.titles).toMatchInlineSnapshot(`
+      {
+        "[Measures].[contributors.COUNT]": "Custom title for contributors.COUNT",
+      }
+    `);
+  });
 });