Move multiple crossfades at once?

I swear I've done this before in Reaper but I can't get it to work now! Is there a way to select multiple items on the same track and slide all of the crossfades around at the same time? Really simple what I'm trying to do, vid here explains it:

I'm struggling to find this feature too. Please, Cockos, make this happen.

Hi It's in mouse modifiers, enable relative edge edit for moving crossfades. .