It is documented. Make sure that you have show for Firefox 4 selected. You should see "Tab Groups View Ctrl+Shift+E" at the end of the Windows and Tabs section.

You can see that shortcut to open Tab Groups if you click the "List all tabs" button at the right end of the Tab bar

I don't think I understand your reply. Or perhaps you misunderstood my question.

I'm not after the "Tab Groups View Ctrl+Shift+E" shortcut. That only goes to the Panorama view (ie, the view that shows all the groups). What I want is to switch immediately to the last viewed tab in the next tab group. That shortcut is "ctrl + `". I still can't see that anywhere on that page.

It's a wiki, so anyone can make the edit. I've added "Next Tab Group" and "Previous Tab Group" (with the Shift modifier), but my changes need to be reviewed and approved.

The funny thing is that I found this hotkey by accidentally hitting it when going for Ctrl+Tab. I'd read the hotkeys list when Firefox 4 was released, but I didn't remember it being listed here.

I guess my question wasn't "how do I add to the support page?". My question was "why doesn't mozilla properly document their product?". Which is nicely demonstrated by the second part of your response - you had to stumble on the shortcuts rather than have them already documented by mozilla.