Per-light settings for Lightmass
Editor Properties: (see get_editor_property/set_editor_property)
indirect_lighting_saturation(float): [Read-Write] 0 will be completely desaturated, 1 will be unchanged
shadow_exponent(float): [Read-Write] Controls the falloff of shadow penumbras
use_area_shadows_for_stationary_light(bool): [Read-Write] Whether to use area shadows for stationary light precomputed shadowmaps. Area shadows get softer the further they are from shadow casters, but require higher lightmap resolution to get the same quality where the shadow is sharp.