Well, seems like the list of CMap export formats and the list of yEd import formats are disjoint. Unless one of CXL, XTM/XCM, or IVML is actually an XML format, it is not possible to import CMap files.
(If one of the aforementioned formats is an XML format, then you need to write a XSLT that transforms the CMap file into yEd's GraphML.)