I was giving a talk at Trier Digital Humanities Autumn School 2015 on Luhmann’s way of working with his Zettelkasten, and how I implemented this technique in the electronic Zettelkasten.
The core principle of Luhmann’s way to manage his notes was a combination of selective tagging, manual links between notes and a sequence of short notes and arbitrary branching („diversification“) of note sequences (see also described in this post).
To my best knowledge, there are hardly any (or even none?) tools that facilitate this workflow, except for the Zettelkasten. Please add your comments, if you know tools, or have built your own workflow that imitates Luhmann’s Zettelkasten-technique.
If you like, you can download the slides of my talk here: Introduction to Luhmanns Zettelkasten-Thinking (PDF-slides).
Strenge Jacke! 
Hat dies auf staerken | klaeren rebloggt.
How about Connectedtext? It seems fix with Luhmann’s way of taking note too.
As far as I know (and have tested ConnectedText), it supports manual linkage (Wiki-like), however, it does not facilitate note sequences and arbitrary branching of these linear note sequences.
Hi,
if I dont misunderstand the Zettelkasten concept, the following two tools have a very similar background idea: zotero (free, open source) and devonthink (mac only).
Both implement a fulltext search; you can create notes manually or add websites and pdf files.