Tree style tabs is a vertical tab extension for ff and the best ui around if you use a lot of tabs. I can't even use chromium vertical tabs anymore because they feel terrible in comparison. You can also fully style tree style tabs via css.
>>eyegor+(OP)
But then you get duplicates, since Mozilla made it a pain to disable the main tab bar. I'm using a Chromium offshoot (Arc) but I also like how Vivaldi handles vertical tabs. Firefox doesn't just compete with Chromium itself, but the entire ecosystem.
>>tapoxi+v5
Does Vivaldi nest tabs yet? Its been a few years since I tried it but it didn't use to.
With TST, I can open a link as a new tab (middle click) and it is shown as a child of the opening tab. This makes it easy to minimise or close a whole tree of tabs.
>>aemble+an
you can stack tabs in a group, and when you're inside that group, new tabs are opened within that group, but not sure about the middle click for a single tab
It also has a great alternative - workspaces, that helped me much better vs. the stacking, that for some reason didn't stick