How do I merge tests created from separate imports of the WADL?

I created a project from a WADL.  I filled out some of the tests, and then I continued developing my app, which meant adding more services to the WADL.  Over time, as there didn't appear to be any way to "refresh" the WADL import, I simply had to import it again, which created the entire tree again, with the additional services from the last time I imported it.  I now have several parallel trees, each with similar sets of services.  I'd now like to merge all of the tests that I created into a single tree.  Unfortunately, dragging anything from any level of this tree to any other level doesn't appear to work.  The drag icon tells me there is no valid drop location for anything I drag.

I'm using soapui-3.0-dist-24-2009-08-09.