I’d find it useful to be able to add comments of some kind to text in notes - in such a way that they can also be hidden from view, but with a visual indicator that the comment exists.
It would be good if comments could be created markdown style, perhaps by enclosing the comment text between two sets of curly quotes: {{comment text}}. After typing, the comment would disappear, just leaving {}. Hovering on the {} would show the comment as pop up (like a url or an image in a browser, where hovering shows you the link or alt text), clicking on {} would reveal the comment in the paragraph for editing.
It would be useful because I often find when I’m writing I want to comment on the text, but I also want to be able to read the text without being distracted by comments.