Hello,
You have two options,
1. It is possible to copy elements between app models (or at least it has been for the last couple of years)
2. What I have done before is was the time consuming job of exporting both objects as XML, opening them in notepad++, and then manually copying accross the XML for elements I wanted.
Worth noting - best practice is to have lots of small objects for each system rather than big objects with lots of actions. So it might be better practice to keep your objects seperate and attach.