I tried using your advice but this method still does not work. They way the example files are set up in there is a silicon ring drawn in Lumerical and then the background material is etched out of it by drawing subsequent rings for the gratings in a different material. So exporting to GDS based on the height argument alone does not work as the silicon ring geometry object and the etch geometry objects have the same height in Lumerical for a fully etched geometry ( eg. the silicon is say, 0.5 um tall, but the etches are 0.5um tall as well just a different material)
Do you have any other ideas how to export this properly to GDS for a fully etched grating using the example files? Is height of the geometry object the only argument that is possible to export upon?