All functionalities of old versions of SHP Designer should work in the new ones. This is not the case. Why?
In SHP online, a workflow made with SHP Designer 2013 starting a functionality on an item created by a workflow SHP Designer 2010 is not detected to start automatically. The problem is that a lot of functionalities of SHP Designer 2010 don't work with SHP Designer 2013 anymore. So, you can't do anything else than using a mix of both versions.