For each process that has sub-processes, PowerDesigner can create a default control flow linking all of its sub-processes in a business process diagram.
The control flow is automatically displayed in a business process diagram. The flow contains a start and an end with all the sub-processes linked by flows between them. Note that only the first level of the hierarchy is displayed. You can further refine the control flow by creating other objects in the diagram.
For more information, see Building Business Process Diagrams.