At a loss for how to connect sub processes

Hi…hoping someone more experienced with BPMN than I can help. I’ve spent a lot of time looking into how I can connect two sub processes and I’m at a loss. In Camunda, you CAN link two processes. I get this. However, if you can’t do it at the task level within a sub process I can’t see how you know what the touch point is between sub processes. Example…I have two swim lanes. I have a bunch of tasks within an expanded sub process. However, as part of this process I have lane 1 sending a document for review to lane 2. It’s all part of the same sub process but yet I know you are not allowed to link at that level. One, I think this is dumb, why wouldn’t they prevent this? Second, knowing I can connect sub processes but only at the highest level, how do I still call out where exactly the tasks cross swim lanes. If I can’t show this then someone will rightly ask, why doesn’t the diagram show ‘how’ the sub processes connect.

I get the impression that you may be confusing the concept of lanes with that of pools. Can you upload some process models to help explain the problem better?

I’d like to but I can’t see where this forum let’s you upload files? I get where you’d think that but that isn’t actually the case. I have the pool as the ‘parent’ process with lanes being participants. This way I have a sub process taking place only within 1 pool. I have a second pool just like the first with a sub process. so far so good. the problem is and perhaps this is a bpmn rule, the two processes connect to each other but camunda will only you to connect a sub process to a sub process. It will not allow you to draw the line from the task within sub process A to task in sub process B. so, while you know that the processes are connected, you don’t know exactly at which step or point in the process.

You can use this button to upload files:

I think what you’re asking about is message flows between pools. something like this:
https://cawemo.com/shares/39502d78-7b78-40f5-bd3f-430cd5b9e9a4