I've been running the side-bar version of tab center with this userChrome.css fix but the best I can say about it is that it's "alright". The window close/max/min buttons are just not positioned very well on macOS.
Also, if you hide the sidebar header I think you run the risk of accidentally opening the bookmarks sidebar and being unable to get back to your tabs.
2. cd chrome or create the directory if it isn't there
3. Inside chrome, open userChrome.css or create it if it isn't there
4. Paste the following:
5. Restart Firefox---
1. http://kb.mozillazine.org/Profile_folder_-_Firefox#Navigatin...