Hmm, there shouldn't be any new scrolling and blinking. The Bookmarks Toolbar has a very basic design of fitting a certain number of bookmarks followed by a ">>" button to show the rest. It doesn't scroll. Or is this a problem on the tab bar at the very top? There was a thread where the tab bar kept shifting because a tab was opening and closing. Could you review this thread on jumping tabs and see whether it sounds like the same issue: https://support.mozilla.org/questions/1364259 ---- More generally, could you test in Firefox's Safe/Troubleshoot Mode? In that mode, Firefox temporarily deactivates extensions, hardware acceleration, any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem. ''If Firefox is running:'' You can restart Firefox in Safe/Troubleshoot Mode using either: * "3-bar" menu button > Help > Troubleshoot Mode... (before Fx88: Restart with Add-ons Disabled) * (menu bar) Help menu > Troubleshoot Mode... (before Fx88: Restart with Add-ons Disabled) and OK the restart. A small dialog should appear. Click the Open button (before Fx88: "Start in Safe Mode" button). ''If Firefox is not running:'' Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.) A small dialog should appear. Click the Open button (before Fx88: "Start in Safe Mode" button). ''Note: Don't use the Refresh without first reviewing this article to understand what will be deleted:'' [[Refresh Firefox - reset add-ons and settings]]. Any difference?