It also means that what my plugin does is much less “diagram-y” than PlantUML or Mermaid: there are no cross-reference lines, no different colors, no varied line types, and so on. It’s simply a way to display hierarchical Markdown—and within the boxes, potentially anything Obsidian can render (in the future). Essentially, it’s just Markdown textboxes arranged hierarchically in a convenient layout. (That’s why it’s suited for literature excerpting.)
Converting this into basic Mermaid or PlantUML shouldn’t be too difficult; because it’s basically just bullet points and indentation. A piece of cake, I guess. But perhaps such a conversion would be better implemented as a separate plugin—one that transforms outline hierarchies into various diagram types. If I tried to include all those features diagram software has, it would end up cluttering the outline Markdown quite a bit with code. (If anyone has ideas on how to avoid that, I’d be happy to keep adding more diagramming features.)