Huh for once I'm advocating for the use of LLMs lol. Anyway, you could have an LLM go through notes and try to sort them by topic. It seems notes and topics have a many-to-many relationship. And you could have people maybe comment on a given note-topic relationship to explain how they accurate they feel it is? Or maybe, topics are things different users create that they can share with others. Each user can assign a note they feel belongs to a given topic and then when you search by topic, you get user submitted groupings of notes? Then another user could copy that grouping of notes, change the topic name if they like, add/remove notes to the grouping and then publish it again? Idk I'm just spit balling 

 Expensive