Well, I'm sure there is a way to view
ALL the notes of the piano in the MIDI Piano Roll, but I could not find it.
I got frustrated and decided to fix it my way right now.
So, I made a TXT file that can be used in the Reaper Midi Editor:
Find it here in the stash:
https://stash.reaper.fm/v/35025/Pian...ll%20Notes.txt
Download and Save the txt file on your hard drive.
Open the Midi Editor
Click: File --> Note/CC Names --> Load Note/CC Name from File --> (find the TXT file on your hard drive).