I have come across XSLT options in editing XML documents, but haven't worked with it as a translation/transposition editor. I would probably try something cruder like a pair of spreadsheets where I'm copying/pasting columns.
That brings me to a related question: is there a bulk import facility for yEd? I see there's an Open option for Excel files, but am wondering how to add nodes/edges in bulk to an already open file; merging new data with existing.