This is driving me nuts; there must be something I'm missing.
 
I have several clips of snare hits (rolls) in a MIDI track. I've opened the PRV, and slid open the velocity pane. I can ONLY see the velocity levels for each note in the pane if I select the clip - which selects ALL the notes.
 
I need to adjust the velocities for a couple of notes in the clip - but if I use the mouse to adjust the level, ALL notes in the clip are adjusted for velocity. If i un-select the clip, I no longer see the velocity values.
 
What am I doing wrong? 

I think I found the solution in this youtube video here:
link
 
The NOTES menu in the PRV view has a drop-down list of options including [X] Show Velocity on Selected Notes Only.
Clear that checkbox, and we're good to go.
 
I hope this helps someone out there.