PS. also worth noting that Opera allows for easily grouping of tabs in the manner similar to the one described in OP (no naming though, fortunately (in my opinion at least)).
What would work is putting a plus next to the closed tabs button (trashcan looking icon) along with the current plus at the bottom of the tabs.
I agree with you on the naming. I don't want to have to name each group. Although it would be nice to add it, possibly after a group has been created, then be able to right click no the group and give it a name so that the name shows instead of the "top" tab.
I just tried it and it seems that there's a sweet spot around 5-6 tabs where the button is partially hidden, but after that thumbnails are removed and you can see it again. A slight problem, but nothing to worry about.
> or that you can't switch easily between thumbnails/no-thumbnails view
Right click -> Customize -> Enable thumbnails in tabs.
Edit: just checked it again (placing tab bar on the left) and now thumbnails turing on/off doesn't work at all - like I wrote: "buggy" :)