Add more UTM tiles after creating UTM tiles in TRainzDEM?

I used TrainzDEM to import OpenStreetMap images into a new route/map using Map Tile Server. I tried to create UTM tiles but TrainzDEM didn't generate all of the UTM tile objects even after drawing route lines. I tried to create more UTM tiles but the "Export to Trainz UTM tiles as Overlay Objects" dialog box doesn't let me create new map name. If I choose the existing map name, a dialog box asked me if I want to make changes to the map. What shouid I do?

I think that TrainzDEM can't create more than 32 X 32 UTM tiles so I can't create entire street map of New York City. Also, the default lighting is too bright.