I released the first version of my IBIS notation editor to the Mac App Store today. Over the next weeks will I need to polish it and beautify the supporting material like screenshots, etc. But have a look here: https://kneupner.de/software/visual-thinking-ibis
So what is IBIS? I found this page as an introduction. The same author did one more blog on the topic. The author (Chris Tomich) did a good job. If you want to understand more, read the book from Paul Culmsee and Kailash Awati.
I disabled the comments for this blog post. Please comment on the software page.