If you’re running #Firefox (or Firefox derivatives like #Librewolf) in space-constrainted environments (e.g., while presenting at 1920×1080 resolution @ 200%, which is what I usually do for streams and which I’ll be using while doing my live coding session with #Kitten at @newcrafts in Paris next week, this #CSS hack lets you smoothly auto-hide Firefox’s #chrome to save valuable vertical space:
https://github.com/MrOtherGuy/firefox-csshacks/blob/master/chrome/autohide_toolbox.css
Make sure you follow these instructions first: https://github.com/MrOtherGuy/firefox-csshacks#setup