Error Event Definition

Hi there,

Im using a modified version of the properties-panel example.
When you an error boundary event, it normally creates an in the bpmn and the code of that error is associated to the event in the field errorRef.

Want i want to ask is how do i modify this in order for the errorRef being defined manually by the user?
Reason: the bpmn files are read by activiti (modified) and the errors given need to be only errors from our system (that will be listed to the user in bpmn-js in a select box).