Hi Arlo,
I've tried the option with plain text in the notice box, but I didn't get a suitable format. In Settings there is an option to set Lyrics Font to monospace, which could help. But this does not work for the notes field, just for the songtext.
Another option would be to add the key numbers to the notes field, e.g. A0 to B1: Bass-Synth, C2 to G5: E-Piano, A5 to B6: Organ a.s.o.
But to be honest, I prefer the picture

So for now I copy my keyboard layout to the document or maybe add it as additional document.
However, thanks to put to the wishlist !!