In diagrams of the Enterprise BPMN collaboration diagram type, you can assign multiple models to a Call activity object.
You can expand a call activity.
Procedure (quick video)
You have expanded an object of the Call activity type. The objects of the assigned processes cannot be depicted if multiple enterprise BPMN collaboration diagrams are assigned. The lock symbol is displayed instead.
Tip
You can expand an object of the Call activity type by clicking the symbol Expand.