It is now possible importing and exporting the navigator favourites.xml file. The GPSBabel program contains the Navigator scheme from version 1.5.0. The GPSbabel conversion program can be downloaded here:
The Navigator scheme has been added to the GPSBabel program upon my request as I needed a program that could do this conversion. I thank the programmers behind this program and the people here in this forum who provided me with the information about the format for lat and lon stored in favourites.xlm
So if you also need to convert the favourites.xml file try the GPSBabel program.