I used sidebery and edited the userchrome.css using guides from r/FirefoxCSS
here's some guides for them:
- https://www.reddit.com/r/FirefoxCSS/comments/rmi8dg/yet_another_sidebery_setup/
- https://superuser.com/questions/1268732/how-to-hide-tab-bar-tabstrip-in-firefox-57-quantum
But for reference, here are the codes for them (since Reddit appears to be down at the time of this writing)
Here's the sidebery link on github
https://github.com/mbnuqw/sidebery
Note, to find your firefox profile folder: