Notes can also be added to any item in your watched history, collection, or ratings. Hover over a poster and you’ll get a button to Add Notes along with privacy and spoiler settings.
The “hover over poster”, to add Notes to items, works on “Movies” or “Episodes”, but not on “Shows”, when option is selected on dropdown menu.
It was my intention to add a Note to a Show, on my Collections page, using the hover Add Notes, but that only appears on the individual episodes of the show.
Apparently I need to go the specific Show page itself and then add a Private Note there, which then appears on the top left corner of the poster, just not my desired outcome insofar as consistency of the Notes display on my Collections page,