In this particular use case we didn’t need to identify whether it’s a note, we just needed a workflow to trigger whenever a note was added.
The actual workflow utilises custom code modules that obtain the “hs_note_body” values for all notes on a contact, then checks if the string values contain any text that matches a specific RegEx statement. If no matches are found it ends, or if any matches are found it modifies the “hs_note_body” values for those notes and updates them.