Ublock Origin is an obvious one, but I also can’t stand not having Foxy Gestures anymore. It adds customizable mouse gestures, so you can set it up to have easy swipes to go back a page, reload a page, close a tab, etc, and it feels wonderful and smooth to use compared to just using the traditional buttons to do everything. Honestly it’s kinda wild to me that this isn’t more popular now that people are so used to phone gestures. It’s good for the same reasons!
FoxScroller, I like to scroll pages while practicing music, which always impresses people. Gesturefy, gotta have those mouse gestures. With a tiny Windows program called NeatMouse I can do it all with the keyboard, too. Kinda off topic. Imagus, what is this clicking and opening crap? SessionSync is good for saving your tabs. Fun to see what you were wasting time on 5 years ago.