As IainB says in his onenote threads, the problem with the zettl is that it doesnt include images, videos, etc. It's centered around text. And his method of using onenote to me is much nicer/easier/better for software than zettel would be.-superboyac
The system does include images, videos and anything else that's used. But they are resources that the cards link to. So you could have film that you were analysing. you would do a card for each thought about the film and put in a link to the film presumably noting the point in the film you were referring to (assuming it one a single point). You have your card index and you have your resources. Not the same thing.
And if your thought was visual, then you could draw it on a card.
The system was designed by an academic for his academic work so most of the content is naturally text. But wouldn't have to be that way for someone else.
I'm sure you
could do the system on OneNote. But I very much doubt it would be as effective as the original, even if it were Luhmann himself doing it.
Software naturally shapes and restricts the thoughts that come when using it. The more feature full the software is, the more the thinking is moulded into the shape of the program.
I believe that this is the problem I see with much of the discussion of the system. They see the wooden box, they see the cards with unique numbers, they notice that the numbering system continually forks, they notice that cards can contain references to other cards, they notice that they can contain references to source materials - and the discussions I've seen imply they believe that this is the system.
It can't be the system. It's just a tool. The interesting bit, assuming there is one, is how the tool was used and what made it better than other possible tools. Much of that will have been in Luhmann's head. He did write a bit about the system. Presumably he talked about it. There might be other clues in that, though I doubt he was able to describe the intricacies of the relationship between his thinking and writing and the tool he had developed over thirty years. Each card is for a thought, not information - information is external in the sources.