Another vote for this feature - I'd love to permanently switch to Firefox on mobile, but it is significantly less usable than chromium browsers due to lack of tab grouping.
Just adding my vote here. I badly want to switch to FIrefox permanently, but I really can't live without that beautiful 'open tab in new group' feature that Chrome has.
I desperately want this feature so I can sync my computer with my phone. The lack of tab grouping is the only reason I'm still using Chrome. I have tried multiple times to use firefox, but because I use so many tabs (stackoverflow, c# documentation...) that my screen just gets cluttered and I can't get to any tab in a quick manner.