Firefox .css tweaks

here my take on Morrolinux's minimal firefox https://gist.github.com/morrolinux/87aa37396432ea5d14a9220bc4892100

Enable Firefox features

Go to about:config and set all of the following to true:

    toolkit.legacyUserProfileCustomizations.stylesheets
    layers.acceleration.force-enabled
    gfx.webrender.all
    gfx.webrender.enabled
    layout.css.backdrop-filter.enabled
    svg.context-properties.content.enabled
    
    # LINUX ONLY - WORKAROUND FOR BAR HIDING ON DRAG EVENT
    widget.gtk.ignore-bogus-leave-notify = 1

Write your userChrome.css

1. Find your Firefox profile folder (about:support --> "Profile Directory")
2. Create a folder named chrome inside it.
3. Create a file named userChrome.css inside the chrome folder you just created.
4. Paste in userChrome.css whatever you like from above
5. Restart Firefox for changes to take effect. If nothing changes, try going to about:profiles and click the "Restart Normally" button in the upper right portion of the screen. Thanks @kr1s7ian for pointing this out.

To hide the "classic" horizontal tab toolar entirely

Paste the content of userChrome.css in your local chrome/userChrome.css

And then go to Sidebery settings > General > Preface value, enable it and set it to XXX.

Now You also need to remove indent when the bar is collapsed, or you won't be able to see all tabs

Go to SideBery settings --> Styles editor and add:

#root:not(:hover){
  --tabs-indent: 0;
}

done!