I have a system with multiple subsystems. These subsystems also have multiple parts or assemblies underneath them. 

I have also made a functional decomposition following the magic grid bok p99

For flows at the subsystem level I can use the item flow manager to create item flows and specifying activities without an issue.

When I need to have an item flow that goes inside of a part or action to communicate with a nested element, the item flow manager lets me select the relevant behaviors (Activity1 sending FlowObject to Activity 5)

But then I get a message that there isn't a diagram that covers this connection.

If I click yes, I get a new diagram with control flow going from Activity 1 to Activity 5 and flow object going the opposite way. Also this diagram lives under Activity 1. 

The previous diagram of activity 1 does not have an object automatically defined on its flow like the other item flows.

Is this the intended method for tying structure to behavior? How do i manage this for nested elements that transfer objects from a higher level? I didn't see any specifics on this in the Magic Grid BoK.

Let me know if any clarification is needed.

Please advise.