[Docs] Discover docs updates (elastic#198423)

This PR updates the first few pages of the Discover docs:
- Splits most of the content of the parent page into a child page to
match with the structure of the Dashboards docs
- Refocuses some of the content so that it looks generally applicable to
users and their data rather than a sample data-based tutorial
- Adds missing content flagged in
elastic#192149
- Adds some content updates specific to 8.16 flagged in
elastic/platform-docs-team#500 (I still need
to figure out what's the best way to document ES|QL stuff)

Rel: elastic/platform-docs-team#500
Closes: elastic#192149 
Closes: elastic#162265
Closes: elastic#187417

Note: While there may be more missing features that we want to document,
let's first get these updates in.

Note2: If you're wondering where to preview the changes, find the
preview link in the Github actions comment and navigate to the "master"
version of the Kibana guide.

---------

Co-authored-by: Elastic Machine <[email protected]>
Co-authored-by: Matthias Wilhelm <[email protected]>
Co-authored-by: Julia Rechkunova <[email protected]>
Co-authored-by: Davis McPhee <[email protected]>

docs/discover/document-explorer.asciidoc

@@ -1,43 +1,35 @@
 [[document-explorer]]
-== Explore your documents
+== Customize the Discover view
 
 Fine tune your explorations by customizing *Discover* to bring out the the best view of your documents.
-Adjust the chart height, modify the document table, and look inside a document.
 
 [role="screenshot"]
 image::images/hello-field.png[A view of the Discover app]
 
 
 [float]
 [[document-explorer-c]]
-=== Hide or resize the chart
+=== Hide or resize areas
 
-Hide or resize the chart for a better fit.
+* You can hide and show the chart and the fields list using the available collapse and expand button in the corresponding area.
 
-* To turn off the display of the chart, click
-image:images/chart-icon.png[icon button for opening Show/Hide chart menu, width=24px]
-to open the *Chart options* menu, and then click *Hide chart*.
-
-* To change the chart height, drag the resize handle
-image:images/resize-icon.png[two-line icon for increasing or decreasing the height of the chart, width=24px]
+* Adjust the width and height of each area by dragging their border
 to the size you want.
-The chart size is saved in your browser.
-
-* To reset the height, open the *Chart options* menu, and then select *Reset to default height*.
+The size of each area is saved in your browser for the next time you open **Discover**.
 
 [float]
 [[document-explorer-customize]]
 === Modify the document table
 
-Customize the appearance of the document table and its contents by resizing the columns and rows,
-sorting and modifying the fields, and filtering the documents.
+Customize the appearance of the document table and its contents to your liking.
+
+image:images/discover-customize-table.png[Options to customize the table in Discover]
 
 [float]
 [[document-explorer-columns]]
 ==== Reorder and resize the columns
 
-* To move a single column, click its header. In the dropdown menu,
-click *Move left* or *Move right*.
+* To move a single column, open the column's contextual options, and select *Move left* or *Move right* in the available options.
 
 * To move multiple columns, click *Columns*.
 In the pop-up, drag the column names to their new order.
@@ -46,17 +38,31 @@ In the pop-up, drag the column names to their new order.
 +
 Column widths are stored with a saved search.  When you visualize saved searches on dashboards, the saved search appears the same as in **Discover**.
 
+[float]
+[[document-explorer-density]]
+==== Customize the table density
+
+You can adjust the density of the table from the **Display options** located in the table toolbar. This can be particularly useful when scrolling through many results.
 
 [float]
 [[document-explorer-row-height]]
 ==== Adjust the row height
 
 To set the row height to one or more lines, or automatically
-adjust the height to fit the contents, click the row height icon
-image:images/row-height-icon.png[icon to open the Row height pop-up].
+adjust the height to fit the contents, open the **Display options** in the table toolbar, and adjust it as you need.
+
+You can define different settings for the header row and body rows.
+
+[float]
+[[document-explorer-sample-size]]
+==== Limit the sample size
+
+When the number of results returned by your search query (displayed at the top of the **Documents** or **Results** tab) is greater than the value of <<kibana-discover-settings,`discover:sampleSize`>>, the number of results displayed in the table is limited to the configured value by default. You can adjust the initial sample size for searches to any number between 10 and `discover:sampleSize` from the **Display options** located in the table toolbar.
+
+On the last page of the table, a message indicates that you've reached the end of the loaded search results. From that message, you can choose to load more results to continue exploring. 
+
+image:images/discover-limit-sample-size.png[Limit sample size in Discover]
 
-[role="screenshot"]
-image::images/document-explorer-row-height.png[Row height settings for the document table, width="50%"]
 
 [float]
 [[document-explorer-sort-data]]
@@ -70,7 +76,7 @@ column header, and then select the sort order.
 
 To sort by multiple fields:
 
-. Click the *field sorted* option.
+. Click the *Sort fields* option.
 +
 [role="screenshot"]
 image::images/document-explorer-sort-data.png[Pop-up in document table for sorting columns, width="50%"]
@@ -106,62 +112,18 @@ Narrow your results to a subset of documents so you're comparing just the data o
 
 . Select the documents you want to compare.
 
-. Click the *documents selected* option, and then select *Show selected documents only*.
+. Click the *Selected* option, and then select *Show selected documents only*.
 +
 [role="screenshot"]
-image::images/document-explorer-compare-data.png[Compare data in the document table, width="50%"]
-
-[float]
-[[document-explorer-configure-table]]
-==== Set the number of rows per page
-
-To change the numbers of rows you want to display on each page, use the *Rows per page* menu. The default is 100 rows per page.
-
-[role="screenshot"]
-image::images/document-table-rows-per-page.png["Menu with options for setting the number of rows in the document table"]
+image::images/document-explorer-compare-data.png[Compare data in the document table, width="40%"]
 
+You can also compare individual field values using the <<compare-documents-in-discover,*Compare selected* option>>.
 
 [float]
-[[document-explorer-expand-documents]]
-
-=== Go inside a document
-
-Dive into an individual document to inspect its fields, set filters, and view
-the documents that occurred before and after it.
-
-. Click the expand icon
-image:images/expand-icon-2.png[double arrow icon to open a flyout with the document details].
-+
-You can view the document in two ways. The **Table** view displays the document fields row-by-row.
-The **JSON** (JavaScript Object Notation) view allows you to look at how {es} returns the document.
-+
-[role="screenshot"]
-image::images/document-table-expanded.png[Expanded view of the document table]
-+
-. In the *Table* view, scan through the fields and their values, or search for a field by name.
-
-. When you find a field of interest,
-hover your mouse over the *Actions* column
-to:
-.. Filter the results to include or exclude specific fields or values.
-.. Toggle the field in or out the document table.
-.. Pin the field so it stays at the top.
-
-. To navigate to the next and previous documents, click the < and > arrows at the top of the view.
+[[document-explorer-configure-table]]
+==== Set the number of results per page
 
-. To create a view of the document that you can bookmark and share, click **Single document**.
-+
-[role="screenshot"]
-image::images/discover-view-single-document.png[Discover single document view]
-+
-The link is valid for the time the document is available in Elasticsearch. To create a customized view of the document,
-you can create <<external-plugin-development, your own plugin>>.
+To change the numbers of results you want to display on each page, use the *Rows per page* menu. The default is 100 results per page.
 
-. To view documents that occurred before or after the event you are looking at, click **Surrounding documents**.
-+
-Documents are displayed using the same set of columns as the *Discover* view from which
-the context was opened. The filters you applied are also carried over. Pinned
-filters remain active, while other filters are copied in a disabled state.
-+
 [role="screenshot"]
-image::images/discover-context.png[Image showing context view feature, with anchor documents highlighted in blue]
+image::images/document-table-rows-per-page.png["Menu with options for setting the number of results in the document table"]