When I make a new note inside a normal-note (a note having the normal_note prototype), there’s a 90% chance that I will want it to be a normal-note. But when I drag a collection of notes of various prototypes inside, there’s a 91% chance that I will not want them changed. What to do?

Just see the $OnAdd of normal_note to:

if(!$Prototype){$Prototype=normal_note}