Thank you! Very cool.

I don't see a button for it (on mobile currently, and will check thoroughly at my computer) -- is there a button to add a node?

Another feature I've always craved for code diagramming is "collapse downstream nodes" -- though it might be outside of your scope (and mermaids?).

Hi as of now I haven't added that feature so the current way would be to edit the .mmd text. However I think you are right that would be a good feature to add. For collapsing downstream nodes I think it would make sense with the request the someone else made in this thread for animations. From what I see it should certainly be possible to implement at some point!