iPhone 13 pro max

Notes passwords are per note. Not by folder.

If you have locked Notes in a group or folder in the Noted App, you can remove the lock for each note by doing the following:

1. Tap the locked note, then tap View Note.
2. Enter your password, use Face ID, or use Touch ID.
3. Tap the More button .   
4. Choose Remove.

When you remove a lock from a note, it's removed on all of the devices that you're signed in to with the same Apple ID.

If you don't remember the password you use to lock the note, then it cannot be removed and the note cannot be recovered.

If you forgot a Notes password on your iPhone, iPad, and iPod touch - Apple Support

If you do not remember the password you used to encrypt the notes, they are unreadable. There is no workaround or way to change it without the original password used.