Lock Notes

Unlike some Password managers, the Apple application Passwords does not currently save secure notes.

To create a secure text, use the Notes application. Notes can be shared using iCloud but not in the Keychain.

To lock an open note, tap the padlock at the top of the note. Then use your passcode or a separate password for those stored on your device.

and then use your account password or add a new password to the note.

Or use the menu option File -> Lock Note to lock the Note.

Note that on an iPhone you will need to click on the … at the top and then hit the lock icon.