For completeness, here – in chronological order – are the other screenshots that I took before reverting to a boot environment that includes Firefox 84.0.2.
toolkit.legacyUserProfileCustomizations.stylesheets true (userChrome.css in effect), with the window just wide enough – spanning multiple displays – to show the tools overflow menu and most of the vertical scrollbar:
- there’s inexplicable dead space to the right of the Firefox Account menu.
Within the constraints of a single display:
toolkit.legacyUserProfileCustomizations.stylesheets false:
For test purposes only, I temporarily placed Bookmarks Toolbar Items to the left of the address field:
toolkit.legacyUserProfileCustomizations.stylesheets true:
- fewer items at the top level of my Bookmarks Toolbar folder (not to be confused with the Bookmarks Toolbar)
- I temporarily disabled all extensions – including Multi-Account Containers – that might interfere with the width of the address field
- I temporarily disabled, or pinned to the overflow, extensions that I prefer to not overflow
- going beyond extensions, I removed nearly everything from the areas to the left and right of the address field
- if I recall correctly, this appeared problem-free because the Bookmarks Toolbar was hidden.