From what I can make, the “structure note” is a MOC – sort of like a curated annotated bibliography with extra information sometimes. And an “index inote” s a a list of links on a topic (without so much “value-added” in terms of additional information). But then what is a “hub” note? Are these all used as semi-independent ways of organizing the information or do is one a component of the other?
I think of all 3 as synonyms.