I've not looked directly at Wittgenstein's note collection before, but it could be an interesting historical example.

Might be worth collecting examples of what has happened to note collections after author's lives. Some obviously have been influential in scholarship, but generally they're subsumed by the broader category of a person's "papers" which are often archived at libraries, museums, and other institutions.

Examples: - Vincentius Placcius' collection used by his students - Niklas Luhmann's zettelkasten which is being heavily studied by Johannes F.K. Schmidt - Mortimer J. Adler - was his kept? where is it stored?

Posthumously published note card collections - Ludwig Wittgenstein - Walter Benjamin's Arcades Project - Ronald Reagan's collection at his presidential library, though it is more of an commonplace book collection of quotes which was later published - Roland Barthes' Mourning Diary - Vladimir Nabokov's The Original of Laura - others...

Just as note collections serve an autobiographical function, perhaps they may also serve as an intellectual autobiographical function? Wittgenstein never managed to complete his 'big book', but in some sense, doesn't his collection of note cards serve this function for those willing to explore it all?

I'd previously suggested that Scott P. Scheper publish not only his book on note taking, but to actually publish his note cards as a stand-alone zettelkasten example to go with them. What if this sort of publishing practice were more commonplace? The modern day equivalent is more likely a person's blog or their wiki. Not enough people are publicly publishing their notes to see what this practice might look like for future generations.

Niklas Luhmann thought of the zettelkasten as a cybernetic system.

He considers a precondition of its creation is that it ought to waive any "fixed order", allow for search, and the asking of questions.

There are only the outlines of brief and scant thoughts here however, which would have required significant amounts of additional context not contained on the card. As a result one would require additional underpinning to understand what Luhmann means here as the card definitively couldn't have been directly or easily reused for future writing beyond the basic sketch outline he provides. What proportion of cards have brief thought sketches like this versus more fully thought out and directly reusable ideas within his system? Does Schmidt provide any guidance here without reading portions of the larger corpus? How does this differ from the guidance of Ahrens?

(Translation from German to English via Google)

Schmidt, J. F. (2018). Niklas Luhmann’s Card Index: The Fabrication of Serendipity. Sociologica, 12(1), 53–60. https://doi.org/10.6092/issn.1971-8853/8350

Annotating with Hypothes.is? https://docdrop.org/pdf/Niklas-Luhmanns-Card-Index_-Th---Schmidt-Johannes-F.K_-0rcv9.pdf/

Note that this article is a revised and shortened form of a chapter in Cevolini's Forgetting Machines. I'm tempted to just read that instead...