On version 129 I've been playing with the CSS to make the tabs wider and thinner. Because of some code in tabbrowser.js I couldn't work around with css, it needs user_pref("ui.prefersReducedMotion", 1) for changing max width to not break tab closing.

https://gist.github.com/digitalsignalperson/7e5d4a44fbd7427a...

screenshot: https://www.reddit.com/media?url=https%3A%2F%2Fpreview.redd....