...
4b) Choose to reference Ecore models rather than export them. (TBD: assumed this will create smaller files, however haven't checked this yet)
4c) Choose Process All (TBD: check whether this is really needed, what difference in output is there)
5) Right-click on the exported UML model and create a new Papyrus model (select "New" and "Other..." to enter the wizard).
...