A Firefox userChrome.css that puts the bookmarks toolbar next to the sidebar instead of above it, so the bookmarks toolbar no longer shifts the sidebar down.
This isn't a proper fix and is a hack job on the inside, so don't expect it to work flawlessly.
This code was generated by an LLM, and is therefore ineligible for copyright. To the extent any rights might still be claimed, they are released under the Unlicense.