When I access my favourites, from the standard DO favourites dropdown menu or from a custom button menu, and hold down the ALT key, instead of opening the favourite in a new tab, it switches DO into customize mode instead with the command editor opened as well.
Further, the same favourites command that I have added to a popup context menu works correctly when using the ALT modifier (that is, it opens the favourite in a new tab)
The actual command being run is:
Favorites SHOWICONS USEQUALKEYS NOOPENINTABS
Maybe a bug, dunno, anyway, that's my Friday night story, would love to know if others experience this too