When I right-click a tab group in the horizontal tabs bar or the vertical tabs sidebar, I get the "Manage tab group" context menu. I don't get that when I do the same in the "List all tabs" drop-down menu. What I see when I right-click a tab group in the tab list drop-down is a context menu with 3 choices: "Move Group to This Window", "Move Group to New Window", and "Delete Group". I was looking in particular to save and close the group when I realized I'm not getting the context menu I was expecting.
I get how we ended up having both "List all tabs" and the vertical tabs sidebar, if it looks like the two features shadow each other somewhat if you have vertical tabs enabled. It would be nice though to align these tab groups access points, for consistency.