If unnecessary complexity as a concept were condensed into code, it would be this obtuse add-on. People like it for the same reason they like VS Code, it has an ecosystem of easily bolted in plugins to geek out over but they aren't adding very much (honestly most should have just been options bolted into the original project) and if willing to use userchrome.js still (yes it can still easily be done, more easily than porting a *.uc.js script to an add-on with either manifest version. Looking beyond the first Google result will not cause you to develop a fatal illness so maybe try it sometime, Reddit hivemind drones!) the whole functionality of this flying spaghetti monster of code can be accomplished in less than 80 lines of JS. The Floorp fork of Firefox implements (and finally effectively fixed their implementation to be usable) this functionality, is not so garish by default (it naturally integrates into the browser style and needs no extra ugly CSS selectors specific to it, what a concept!) and doesn't turn into the hot mess of TST's bad implementation of tag nesting (God forbid you try to rearrange those tabs with a mouse without becoming enraged, tried on Linux and macOS, fickle and badly implemented trash on both ) and doesn't have the "Tree Style Tabs" pendejo banner at the top with the unnecessary close icon (if they don't want it in the sidebar, they probably will just remove the add-on altogether, duh).

I know the hivemind loves this extension and so I will get some virtue signaling indignant outrage for saying this extension is garbage so the brave outraging voice of the people can feel like part of the smart crowd for 5 nanoseconds... but its garbage.