Use case or problem
Modern versions of mermaid.js include important functionality like subgraph-to-subgraph linking and subgraph directionality.
Proposed solution
Upgrade version of mermaid.js included in obsidian (and document the included version somewhere? Perhaps in Help → Formatting Notes?).
Current workaround (optional)
Use an external rendering engine for mermaid. Unpleasant experience, as I now need a full node/JS toolchain on each computer I have obsidian on.