This repository contains the necessary userChrome.css CSS code required to revert the new Firefox megabar (introduced in version 75) back to the previous appearance. Most notably, it removes the annoying growing and shrinking effect that the new megabar includes, but it also adjusts the spacing between the address bar items and moves the item type icon back to its old position.
This is an unofficial CSS tweak with no guaranteed support. It may not work on all systems and may be broken by updates. If you are not prepared to deal with the hassle of these types of "hacky" tweaks, DO NOT USE THEM!
Release notes can be found on this GitHub repository.