List Filters - allow single keypress to trigger

[dfay]

With a list filter, where there's a finite, user-defined set of possible actions, it would be convenient to just hit a single key to trigger an action (by default this could be the first character in the action, with duplicate highlighting in the setup).  I'm working on a replacement for the buggy, slow-to-be-updated Mail Act-On , and my muscle memory can't handle hitting return any more than I used to.