Since we will support coexistence between designers, we need an easy way how to perform migration from Stunner to Current Designer.

I see it like this:
1. In Stunner we will have a button in toolbar (near Save, Delete, Rename..) with label "Migrate to old Designer" or something similar
2. When user click on it he/she will be notified that this is one way migration with buttons "Migrate" and "Cancel" or similar
3. If user click on "Cancel" button dialog will be closed and nothing will happened. If user will click on "Migrate" button - save changes dialog will be provided if needed
4. After that Stunner will change file extension from BPMN to BPMN2, close Stunner and open new (renamed) file in old designer.

KrisVerlaenen can I ask you to provide feedback on this Feature request, does it fit our plans?

mstevens1_jira, can I ask you to revise my suggestion, do you have better vision how to do this migration easier for users?