Using Shift-ENTER opens questions in a new tab.
However, the same does not apply to the other options. Could this be extended to any of the options that load a new page? So, hit i for inbox, then Shift-1 to open the first inbox message in a new tab.
Preferably, I'd still like to see this using the native 'open in new tab' modifier key (CMD on Mac for example), instead of using Shift.