Among other things, I am working on more file format documentation for X-Plane 10. Most of the tools you need for scenery are right there in X-Plane 10.0r1, because our art team needed them.
But there is one feature that slid by: a global shadow disable for an object or art asset. I am adding this directive (it will be called “NO_SHADOW”) to a bunch of places in the scenery system. Typical use would be to completely exclude geometry from shadowing, which will also improve performance (less work for X-Plane to do). The directive will be available in 10.05.
There is one exception: you can disable shadowing in an airplane by disabling the “shadow” check box in 10.04, and “glass” tagged objects from v9 planes are not shadowed.