Beyond fixing a critical bug, SWITCHYARD-1579 also introduced a new operation type, called SIGNAL_EVENT_ALL. It differs from the existing SIGNAL_EVENT in that instead of signaling one process instance with an event, it means signal all process instances with an event. Both cases are supported in the jBPM API, so SwitchYard should as well.
Note that this change should be super-dee-duper easy. All that has to be done is add SIGNAL_EVENT_ALL to the already-existing drop-down list for Operation Type (START_PROCESS, SIGNAL_EVENT, ABORT_PROCESS_INSTANCE). That's it!