Your post says nothing at all to suggest Luhman didn’t “invent” “Zettelkasten” (no one says he was only one writing on scraps of paper), you list two names and no links
My post was more in reaction to the overly common suggestions and statements that Luhmann did invent it and the fact that he’s almost always the only quoted user. The link was meant to give some additional context, not proof.
There are a number of direct predecessors including Hans Blumenberg and Georg Christoph Lichtenberg. For quick/easy reference here try:
If you want some serious innovation, why not try famous biologist Carl Linnaeus for the invention of the index card? See: http://humanities.exeter.ac.uk/history/research/centres/medicalhistory/past/writing/
(Though even in this space, I suspect that others were already doing similar things.)