I'm having exactly the same issue, when i open "Called element" I don't see any of my processes. For example, I create new package, then 2 processes. Both of them are start->task->end. I want to make second process to be subprocess of first one. So after creating both of them and building the package, in first process i set task type to 'Reusable subprocess' and then go to "Called element' and there isn't any process to choose from. I tried this in multiple packages, always the same situation. Is there any solution to this?
Thanks (also hvala :D )