And you can modify the userChrome.css file to change the UI - https://www.howtogeek.com/334716/how-to-customize-firefoxs-user-interface-with-userchrome.css/ htt

And you can modify the userChrome.css file to change the UI - https://www.howtogeek.com/334716/how-to-customize-firefoxs-user-interface-with-userchrome.css/ https://www.howtogeek.com/334716/how-to-customize-firefoxs-u... I remember doing this on an old version because the font size in the tabs was off and it couldn't be adjusted from the settings.