OK, thank you for the tips!

Yes, it works perfectly fine! Thank you very much!

Hi, urlbar-background is not an id anymore but a class.

Thanks for the info. I always have trouble finding this kind of information. I took a look at the latest commits on your GitHub repository, but I didn't see anything noteworthy...

I can’t say much about the color-scheme issue though

The problem is that choosing the "Dark" theme instead of the "System theme - auto" gives a very different result... Is there a way to force the dark mode of the "System theme"?

Thanks for the tip. It works!

urlbar-background is not an id anymore but a class

May I ask how you keep up to date with these kinds of new features? Do you review the new features page when a new version of Firefox is released? Is there an easy way to find out about these changes in advance?

In any case, you have (once again) been a great help; thank you very much, and have a nice day!

I understand that there will be other changes to certain elements, including the address bar, in future versions of Firefox: to which selectors should I add :where(#urlbar) > to ensure that my code is compatible with future versions?

Thank you very much for your help!

Indeed, my message wasn't very clear. While trying to keep my userChrome.css file up to date, I found this first commit and this second commit in your repository; I deduced that certain elements needed to be updated... but I was wondering which ones. I thought this was due to upcoming changes in Firefox, but I was probably mistaken...

OK, that's much clearer to me now; thank you for the explanation. I'll check what's going on with my search bar. Thank you very much! Have a great day!

the button will stay hidden until you open the panel once - which is a bit tricky since the button is hidden

It's tricky... but it's still doable, since you can always click on the first 8 pixels of the address bar to make the button appear. So I think your solution is excellent! Thank you so much!

the value is set to var(--space-small) so you could possibly just modify that

Yes, that's perfect! Thank you so much for your help!

Thank you very much! It seems to be working perfectly.

If I may ask, I'd have two more requests:

1. In the Library, is it possible to reduce the space between the toolbar (#placesToolbar) and the search fields ("Search History", "Search Downloads", or "Search Bookmarks")? Actually, since I wanted to add a margin to the left of #placesToolbar (#placesToolbar { margin-left: 16px; }), the width of the search fields becomes very narrow when the Library window isn’t maximized...

2. I removed the border from most tooltips to match those in my GTK+ theme: tooltip { border: 0 !important; }. However, the Library’s tooltips still have a border. Is it possible to remove it?

Thanks again for your help!

I think what you want to do for the Library toolbar is to make the search input box flex more that the spacer space:

#searchFilter{ flex: 1000 !important }

I don't quite understand. The CSS for the Library seems more complex (to a novice like me) than that of other parts of Firefox. Is the "flex" property a multiplier? Adding "flex: 1.4" is enough to get what I want... so why should I choose a large number like 1000?

which is only really possible by building Firefox yourself or injecting the style using autoconfig feature.

I've used an autoconfig before... but in this particular case, it's really not worth the trouble for such a small thing. Still, thank you very much for your explanations, which always help me understand a little better how all this works.

That's a very clear and detailed explanation. I had skimmed through a few pages about the flex property, but I didn't really understand much of it. Thank you for taking the time to explain all this to me! It makes a lot more sense to me now.