Overview: Add a metatag that shows images that either have notes or don't have notes. Alternatively, note count rather than note content.
Usefulness: Currently, we have a metatag for searching for images with notes that say a certain thing. The only way to look for images with notes in general is notes:*, which then spams the same image id repeatedly for every note it has; or to use notelocked: to find images with locked or unlocked notes (which does not even seem to work to begin with).
Affected pages: Probably some deep internal stuff, but visibly to us, just the post index.

It's noteslocked:. The cheatsheet has a typo.
...that one's still useless for note searches, though. Since there's plenty of noteless posts that are locked.