[jcims]

Not sure if this has anything to do with what you had in mind, but user veuxdo pointed me at it earlier today

https://www.ilograph.com/

I found it interesting anyway. Everything from yaml, automated layout, drilldown, etc.

[markawesome]

While I'm only interested in an open source solution, the YAML formatting they are using is almost exactly the style I was looking for. That would be a huge improvement to the current tooling available. I didn't see anything though, without signing up, that indicates that this would work well for mindmapping as well and implementing features like summaries:

https://xmind-help.github.io/en/summary.html

[c3c]

I build https://sourcespy.com to achieve the same goal - automated layout, drilldown but also ability to pull up the diagram contents from the code.

[jcims]

Just tried checking it out and the site appears to be down.