With org.eclipse.graphiti.ui.features.AbstractCopyFeature.putToClipboard(Object) and org.eclipse.graphiti.ui.features.AbstractPasteFeature.getFromClipboard() it's possible to copy/paste diagram elements in a same diagram or across diagrams in a same Eclipse RCP Graphiti editor instance.
On the other hand I can not copy/paste between diagrams opened in 2 separate RCP instances. This seems to be related to the use of LocalSelectionTransfer in org.eclipse.graphiti.ui.internal.util.clipboard.ModelClipboard.getLocalSelectionContent().
The copy does place the selected elements in my "system-wide" clipboard, e.g. I can then paste in Notepad++ or so and get e.g. :
Michael Wenz Messages: 1883 Registered: July 2009 Location: Walldorf, Germany
unfortunataly, copy&paste is curently only supported withinthe same Eclipse instance, due to what you already wrote. There is a open bugzilla (https://bugs.eclipse.org/bugs/show_bug.cgi?id=375334) for reworking that but it has not yet made it into development. Enhancing that could be one task within that.
You may try to use your own ModelClipboard implementations though from your paste (and maybe copy ) feature and make use of other transfer implementations there, but I'm not sure which ones could apply here.