Sascha Fast appreciated Lüdecke's ZKN3 application as one of the best for adapting Luhmann's techniques to a digital space, but felt that it could have gone further in realizing Luhmann's principles.
Some of the tension in this debate is that between the affordances of analog (paper) versus digital information storage and tagging.
Paper lacks easy corpus text search while simultaneously requiring additional manual indexing to make up for it. Paper also doesn't have the discovery value of autocomplete. On the opposite end paper forces one to more regularly review physical associative trails through one's past work while digital allows one to skip over some of this review process.