Apple Notes Password Hint
How do I access (see) the password hint for Notes?
This relates to both my Iphone 7 IOS 14 and MacOS Catalina 10.15
iPhone SE, iOS 13
I think hint will appear after the third failed attempt. Try it.
Edit: If you are afraid that you will lose the note, try to create a 'test' note then lock it (make sure to add a hint). Try my suggestion to attempt to fail the password three times and see if a hint will show.