Exactly what I needed! Can you maybe do it so it auto groups by domain? Example wikipedia.org 20 pages open and it automatically groups them?

"Customize Theme" does not work. Every next choice switches the previous one to default. Need fix.

EDIT
That was fast! Now it works. Thanks.

Works exactly as it's supposed to, fantastic.

The only things I'd criticise are that the dark mode is completely black(I'd prefer a dark grey) and the currently selected tab could be highlighted better, but these are just minor details.

this is the best looking and most responsive feeling vertical tab addon in my opinion, thank you!

Simple and gets the job done, the closest you will find to the old IE styled tab groups.

current version used:
https://github.com/asamuzaK/sidebarTabs/tree/master/dest

Obviously it's a bit early to rate, but on the Mac, one cannot "ctrl+click" as this is the same as right click. Expected alternative cmd+click and option+click do not seem to work.