Catchwords (broad or even narrow topics) can be useful, but one should expand beyond these short words to full phrases or even sentences/paragraphs which contain atomic (or perhaps molecular) ideas that can be linked.

We could reframe the atomic as simple catchwords, and make molecular ideas combinations of these smaller atoms which form larger and fuller thoughts which can be linked and remixed with others.

Dennis Duncan (2022) touches on this in his book on Indexing when he looks at indexes which contained portions of their fuller text which were later removed and thereby collapsing context. Having these pieces added back in gave a fuller picture of ideas within an index. Connect this idea with his historical examples.

Great indexes go beyond the catchword to incorporate full ideas with additional context. To some extent this is what Luhmann was doing at larger scale compared to his commonplacing brethren who were operating far more closely to the catchword (tag) level. (Fortunately they held the context in their heads and were thus able to overcome some of the otherwise inherent problems.)

The development of all of this historically seems to follow the principle of small pieces loosely joined.