Because the custom DataNode type introduced in the star diagrams assembly is not a simple shape nodes, you cannot create a toolbox item for it using the ShapeTool.Shape attached property.
Instead, the star diagrams assembly includes a toolbox item resource for DataNode which you can reference using the StaticResource element:
CopyA toolbox group for fixed flow diagram nodes
<ms:DiagramToolBoxGroup Header="Nodes"> <StaticResource ResourceKey="{x:Static ms:StandardStarDiagramToolBoxItems.DataNodeToolKey}" /> </ms:DiagramToolBoxGroup>
Remember to merge the StandardStarDiagramsToolBoxItems resource dictionary.