Currently it's a useless add on.
Yes - in an extant session you can collate your tabs into groups, and even move the group from one window to another.
However - that's it.
No long term saving of the group (eg as a bookmark folder?) or ability to close all the tabs in a group (IIRC), or save them in any way.
4/10 google - a nice start but without further development why even bother?
Biting the hand that feeds IT
