For much the same reason that I like NotePlan, I find that knowing when a note was last touched is very important to comprehending a notes contents. Currently, there is no way to know how old a note is without doing some sort of UI manipulation. The quickest seems to be using the mouse to click on the ellipsis button at the top of the note. This is friction when it comes to how I interact with my notes.

Attached is a note in Apple Notes. At the very top in the center is the last modified timestamp.

I would suggesting adding something like this to NotePlan. Further, clicking on the timestamp could be a one-click way to open the revisions navigation ("View Revisions").