I have a MIDI track (which I have open in the piano roll view, and which is sent to the TTS instrument, which is also open, off to the side)
 
Now in the course of playback, the instrument changes from vocal aahs, to spooky pad, to 12 string guitar, and then back to spooky pad.
 
How can I edit those particular patches, so that instead of the 12 string guitar patch, maybe I want to use a mandolin.
 
I don't see where to do it in the piano roll window, but that seems like the logical place to be able to edit such a parameter.
 
Thanks

If they are actual patches, you can perform an Insert Patch Change from the menu and assign the patch change any where you want on the MIDI clip.

If you open the list editor for that track, you can ferret out the patch change from there too. With midi, there's just no telling what's in there unless you were the original creator.

Yep Alt+8 will open that. You can then filter out the events you don't want if it makes it easier. Patch changes will show as a different colour.