There is a bug in Firefox 138. Currently, the workaround is to switch to the classic sidebar and remove a settings file. This assumes you do not need to use the new tabs-in-sidebar feature. '''(1) Switch back to the Classic sidebar if you have the new design.''' The new design has a button bar at the left of the browser. Here's how: On the Settings page, slowly type ''side'' into the tiny search box to filter the listed settings. This should bring the "Browser Layout" section to the top. Un-check (clear) the checkbox for "Show sidebar". That should remove the launcher. Then press Ctrl+B to open the classic Bookmarks Sidebar. '''(2) Remove the xulstore.json file from your current profile folder.''' Here's how: Open your current Firefox settings (AKA Firefox profile) folder using either * "3-bar" menu button > Help > More Troubleshooting Information * (menu bar) Help > More Troubleshooting Information * type or paste '''about:support''' in the address bar and press Enter In the first table on the page, on the Profile Folder row, click the "Open Folder" button. This should launch a new window listing various files and folders in Windows File Explorer. (''On Mac and Linux, the button is labeled a bit differently.'') Leaving that window open, switch back to Firefox and Exit, either: * "3-bar" menu button > Exit * (menu bar or Alt+F) File > Exit Pause while Firefox finishes its cleanup, then: Right-click '''xulstore.json''' then Rename to something like '''xulstoreOLD.json''' Start Firefox back up again and show the Bookmarks Sidebar using Ctrl+B. Now it should stay open when you exit/restart Firefox. ''To restore optional bars, see:'' * [[Bookmarks Toolbar - Display your favorite websites at the top of the Firefox window]] * [[Restore the Menu bar in Firefox]] * Title bar: [[Customize Firefox controls, buttons and toolbars]]