@nika Some interaction between "Sync Tab Groups" and "Tree-Style Tabs" caused tab group containers to show up _as_ tabs. Some interaction between "Tree-Style Tabs" and "Simple Tab Groups" killed every window not in the foreground when I removed Simple Tab Groups. I don't think "Container Tabs" was involved, but everybody's touting tab containers as the hot new thing and so far all it's done for me is break stuff.
@nika At the end of the day, what I want is a browser that puts the tabs in a column on the left-hand side and the ability to background some arbitrary set of tabs so they're open but not currently visible, so I can leave projects in suspended states while I do other things.