Firefox’s update to version 107 destroyed my custom CSS for multi-row tabs. But the internet has an answer. These are the steps:
- Go to about:config and turn layout.css.moz-box-flexbox-emulation.enabled to “true” (source of this important advice: here)
- Strip out any old multi-row code from your C:\Users\[YOUR USER HERE]\AppData\Roaming\Mozilla\Firefox\Profiles\[PROFILE NAME]\chrome\UserChrome.css file [or create one if this is a fist time]
- Replace it with the code at MrOtherGuy/firefox-csshacks [link updated].
Worked for me.