Should ideally look up the Job from the job field and dynamically include a list of value.jelly blocks; just not sure how to wire up the JavaScript for this.

A potential alternative (requiring a core change) would be for ParameterValue, not just ParameterDefinition, to be Describable (where config.jelly just calls value.jelly, passing it = instance), and these would all have a Descriptor, so that <f:repeatableHeteroProperty field="parameters"/> would suffice to configure a List<ParameterValue>. Not as nice for the user, though.

kohsuke also originally suggested adding ParameterDefinition.createValue(Object) as yet another alternative, but again this is not as friendly to snippet generation.