I don't group related tabs together; I don't have a list of tabs on my screen anywhere and fuzzy finding with ivy-switch-buffer them is sufficient for me.
Unfortunately, I can't answer your other questions because I'm good at closing tabs :p
Thanks for the reply. I imagine I could tag them somehow and fuzzy find on the tag or a tagged subset. I'm actually looking at the Nyxt browser now also.
I'm a freelancer, so I regularly switch between various active projects or future, potential projects. That results in lots of tabs.
Unfortunately, I can't answer your other questions because I'm good at closing tabs :p