Subprocess migration


I want to migrate a process, that I decided to put into a subprocess because it is used by other workflows, so I can reuse it.
The process that goes into the sub-process can be something like this:
Process 1:

Then this is the new process, that was the above process as a sub-process
Process 2:

My goal is, to migrate already existing instances of the Reusable process (Process 1), into the new Process 2, but Process 1 in Process 2 is called by the call activity, so I want Process 1 (sub-process of Process 2) to continue the flow of Process 2 when Process 1 ends. Like somehow I need to tells Process 1 instances that they have now a parent definition.

How can I achieve this behavior, with camunda?