Both the .gvn and .gvw file types come from GeoVisu georeferenced data viewer, so if any kind of export or conversion is possible, it would be done with this software. But it might very well be possible that no direct gvn to gvw conversion is actually possible.
Unfortunately, we have not found any specific information about such conversion, so if you need help with some particular issues, it would be best to contact GeoVisu support or some online community for help.
Updated: January 6, 2023