The consideration of how to structure a topic, therefore, belongs on notes as well – and not on a meta-hierarchical level. We can provide ourselves with a (temporarily valid) overview over a topic or subtopic just by making another note. If we then link from the index to such a note, we have a good entry point. If the overview on this note ceases to correctly represent the state of a cluster or topic, or we decide it should be structured differently, we can write a new note with a better structure and update the respective link from the index.
