I found several older threads saying that in order to change process flow due to exceptions I have to either signal the process from my work item handler or pass the error as a result parameter and then check for errors.
I also found information saying that with 5.3 I can now attach error catch events to all tasks, including service and script tasks. But I currently dont see how I can create a signal for those error catch events to handle.
My goal is to visually represent error handling in my process diagram, to distinguish it from the normal decision flow. Currently I am passing back error messages as result paramters and then check in a XOR node, wether an error occured. However since the same nodes are used for business decisions this is undesirable and I am looking for an alternative.
Edit: I am having another problem with exceptions. When attaching an intermediate catch error event to a reusable subprocess i get a "Event node 'myError'  should specify an event type", even though I set the messageRef attribute. I do not understand this, as I though the messageRef attribute specifies the "type" like it does with signals.