Mermaid doesn’t do a lot of diagram formats. Unlike plantuml/planttext it doesn’t allow graph viz diagrams. Joplin has a PlantUML plugin and I can use this:
bgcolor="purple:pink" label="Scrum App" fontcolor="white"
subgraph cluster1 {fillcolor="blue:cyan" label="Press" fontcolor="white" style="filled" gradientangle="270"
node [group=g1 packmode=array_c3 shape=box fillcolor="red:yellow" style="filled" width="80%" gradientangle=90]
Undone;
node [group=g2 packmode=array_c3 shape=box fillcolor="red:yellow" style="filled" gradientangle=90]
"Done Done";
node [group=g3 packmode=array_c3 shape=box fillcolor="red:yellow" style="filled" gradientangle=90]
Done;
}
edge [style=invis];
Done -> "Done Done"
"Done Done" -> Undone
}
At least diagrams.net does free format diagrams.