The is no delete.
Discussion
If you're on Amethyst, you can request deletion which relays to the nodes to remove the note.
Besides that, as far as I know there is no proper delete button, more than likely a note might still be broadcasted on other relays if they don't receive the delete notification.
No guarantee nodes will honor deletion requests though so its functionally more like an edit.
Dang so you really gotta be careful of what you say here lol