I have a guitar library that wants aftertouch for vibrato, but I have only weighted hammer action keyboards so no aftertouch. I could assign it to a foot pedal but I already have a Roland PK-6 and a sustain pedal so I'm running out of feet 

Below the pianoroll view where you normally see velocity I can hit the little + icon to add another row of controllers, but how do I select what midi data to assign it to?

When I hit the plus icon to add another controller, I just get another row of velocity with no options to change it.

EDIT: Duh, Hit edit and "new value type"