I couldn't find a work-around to this as not saving it was causing problems in MappedPropertyPortletController if what I was adding to the "containedDataDefinitions" map was a PersonDataDefinition instead of a PatientDataDefinition.

I tried to debug this and found that ParameterizableUtil.getParameterizable(mappedUuid, mappedType) returns null if the definition we are adding  is a PersonDataDefinition.