This is a new feature of the Microsoft Edge browser. Simply enable the sidebar in Settings, then go to https://pwa.kiwix.org, click the plus sign in the sidebar, then "Add current page". More info after the demo.
See also: [ Demo of all OPFS features ]
You may need to adjust the width of the bar so that all the icons fit. You can also reduce the size of the UI in Configuration if you'd like a snugger fit. Please note that the current icon is white, which means it is more visible if the Edge theme is set to "Dark". We are looking into adding an outline to the favicon that is used in order to make it more visible in light mode.
Please note that due to a Chromium bug (which also affects extensions), folder picking is not available in the sidebar, so please simply pick the file you want to load rather than picking a folder of archives. The Edge sidebar works very well with the Origin Private File System, because there is no need to pick or authorize file access.