Firefox issues

try turning off your bookmarks toolbar

ah but it's the bookmarks toolbar i want the compact to affect. Is that not possible to change then?

i can't confirm it myself because i'm running ESR but apparently setting browser.proton.enabled to false in about:config unfucks things a bit

enjoy it until mozilla inevitably removes it next version

There is also browser.uidensity that should be set to 1 (if it isn't already)

xp, chih, tried it and things got even more compact :)

I think Ste meant the Bookmarks dropdown menu from the menubar was no longer compact. I decided to test disabling all Proton entries in about:config and discovered the one that fixes the issue by resetting to how it was before.

set to false:
browser.proton.contextmenus.enabled

and while were at it we might as well set the entry chihuahuau mentioned to false as well:
browser.proton.enabled

i dunno if this is new but i'm forever closing tabs i don't want to close.

the visible tab is highlighted in a lighter colour than usual, the tab the mouse is over is highlighted using a darker colour than usual. it's easy to glance up, see a highlighted tab and hit middle button to close it without registering it was the wrong kind of highlight.