I support this as well. Saving and Closing a tab group enables a workflow where you have a tab group that is relevant only in certain contexts. I use this a lot for TTRPG games, where each campaign is its own tab group. I should only have to have those tabs open whenever I am currently doing something about this campaign, therefore all other groups are closed. When I open Firefox on any synced Firefox, I want to be able to open any closed tab group, work in it, and Save and Close it again. When I move to another device, my changes should be visible there. Currently this is not possible—only open tabs are synced, so I need to at least have all tab groups open and collapsed (which takes up a lot of screen estate, since I can't even group the tab groups) and Sync only covers the tabs themselves, not their grouping info.
