Follow these rules when defining structures in Stateflow® charts:
You must define each structure as a Simulink.Bus object in the base workspace.
You cannot define structures for Stateflow machines.
Note: The Stateflow machine is the object that contains all other Stateflow objects in a Simulink® model (see Stateflow Hierarchy of Objects).
Structures cannot have these scopes: Constant or Data Store Memory.
Structures of parameter scope must be tunable.
Data array objects cannot contain structures.
Structures cannot contain arrays of buses.