It would be nice to get some kind of official confirmation that the ability to add custom CSS isn't going to go away, given that the justification for dropping compact mode seems to basically boil down to it being hard to discover, and Mozilla assuming (without user metrics) that nobody uses it.

How much harder is it to discover the ability to write custom CSS? Do we know that Firefox won't apply the same logic to that feature?

for now.

given this trend of removing little usability and customization abilities here and there, one can only assume the custom CSS will be removed as well. especially seeing as its label has "legacy" right in it's name: toolkit.legacyUserProfileCustomizations.stylesheets

they'll give some reason like "only 1% of users use it" or, "it'll take too much time to make it work with our new, annual UI redesign/overhaul"

that being said, I'm sure someone (either on github or on reddit in /r/FirefoxCSS) will have the necessary custom CSS written to reproduce as soon as the version removing it hits the stable release

I shouldn't have to hack Firefox with custom CSS to get it to behave in a reasonable way.

I use Firefox for multi-row tabs. First it was an extension but now you can accomplish the same thing with CSS.

Of course, every major redesign of the browser breaks the CSS for multi-row tabs and I need to find people who have fixed it and hack it back together. One of these days they'll probably break it completely and I'll switch to another browser.