Toggles pre rendered lightmaps. If the scene has pre rendered lightmaps, the engine will automatically load and apply them. Notice that lightmaps are only rendered when static entities are affected by static light sources.
Lightmaps can be saved into bitmap files from the Scene Editor by simply pressing the Save lightmaps to file button. It will create a directory named scenes/scene-file-name-esc/
and place all bitmaps there.