Makes your Firefox bookmarks bar slide out only when you hover over the navbar, making it look more clean and simple.
This tweak existed ever since 2011 in userstyles.org, with fixes and adjustments applied every time Firefox version went up and introduced breaking changes. Now it lives here.
This is guaranteed to work on macOS only! You'll have to manually tweak px values if you want to make it work on your non-macOS environment.
Please refer to this wonderful guide at userchrome.org for how to set up your own userChrome.css file to enable customizations for the Firefox UI.
Once you have a blank (or existing) userChrome.css file in your Firefox profiles folder, copy-and-paste the code included in the sliding-bookmarks-bar.css file.
As a bonus, if you want to show only icons on your bookmarks bar to make it look more compact (see the GIF image above), copy and paste the code in compact-bookmarks.css file in the same userChrome.css file as well.
MIT License