I started to look at it again a few days ago, and I think I’m on the right track to post something soon. 
It’s more work than expected.
On a technical side, Discourse relies on the Markdown-it library to handle markdown and has many custom plugins attached to it.
In my previous video, I used the library from a CDN link. However, markmap, by default, tries to load Markdown-it from a CDN and use another instance. This means you won’t be able to use specific Discourse features in a markmap, so you must implement the library differently to use the instance from Discourse.
Stay tuned. 