Current support for state machine diagram comes with the support of mermaid and plantuml.

Both are a bit missing.

• plantuml support is done by requesting the plantuml API, which can get overloaded
• mermaid support is a bit weird, as it is more a graph than actually a state machine diagram: Finite State Machine Diagram mermaid-js/mermaid#152

It would be great to add a "native" state diagram support, by including the appropiate library like in flowchart and sequence.
One could use one of these libraries: https://github.com/sverweij/state-machine-cat or https://github.com/jaime-olivares/yuml-diagram

BTW: If this seems to be needed/wanted I could work on this.