Firefox 116.0, See All New Features, Updates and Fixes
https://www.mozilla.org/en-US/firefox/116.0/releasenotes/
https://www.mozilla.org/en-US/firefox/116.0/releasenotes/
Press Ctrl + B for the Bookmarks sidebar.
Press Ctrl + H for the History sidebar.
My guess is we'll have to modify the userchrome.css file again to put the stupid tabs back where they belong, yet again.
Shocking that an interface explicitly not designed to be stable changes release to release. 🤔