New track import/export work flow:
1. Import your track from 3ds/obj into blender.
2. Export it as jpk. Only textured meshes will be exported. A default list.txt will be generated.
3. Import jpk into Blender. the objects will be assigned to groups according to their properties.
4. Modify the groups of the selected object
ctrl+g. If an object belongs to multiple surface groups the first surface is used.
4.1 If required create additional surface groups "surface-[0-9]". You will have to extend the surfaces.txt of course(is not created automatically atm).
5. Export jpk. The group settings will override object properties.