The development version now allows to reference classes from in one PSM diagram from other PSM diagrams. The aim is to imitate the import/include constructs of XML Schema, each PSM diagram should correspond to a separate XSD. To add a reference to adiagram
click "Add reference" in the PSM toolbar and select the diagram. Other properties can be edited after doubleclicking the title of the refernce box on the diagram (green visualization).
After adding the diagram reference to the PSM diagram, structural representatives can reference classes in the referenced diagrams.