Hi,
I whish it was possible too, but I am not aware of anything like that. I resort to the following:
I create a prefab, with a fsm, with NO logic, and simply declare in there my gloval events.
note that it's not always necessary to drop that prefab in the scene, but if you don't get them global event listed, it's because playmaker hasn't scanned the assets, so simply drop it in the scene, and they will register for you to work, once a fsm links to this event, then it's ok, the prefab is not required anymore to be present in the scene.
look at the photon implementation, it uses this trick: check out the prefab "PlayMaker Photon Proxy"
bye,
Jean