The event-based gateway is currently not yet supported in the graphical editor, but the engine does support it. You can take a look at some examples here: https://github.com/droolsjbpm/jbpm/tree/master/jbpm-bpmn2/src/test/resources
https://github.com/droolsjbpm/jbpm/tree/master/jbpm-bpmn2/src/test/resources (BPMN2-EventBasedSplit*.bpmn2)
Kris