So it's safe to say the commands for advanced terrain are as follows:
LOAD TERRAIN Filename, Terrain ID
SAVE TERRAIN Filename, Terrain ID
BUILD TERRAIN Terrain ID
MAKE OBJECT TERRAIN Terrain ID
SET TERRAIN SCAL Terrain ID, X, Y, Z
SET TERRAIN SPLIT Terrain ID, Split
SET TERRAIN TILING Terrain ID, Tile
SET TERRAIN HEIGHTMAP Terrain ID, Filename
SET TERRAIN TEXTURE Terrain ID, Base Image, Detail Image
SET TERRAIN LIGHT Terrain ID, XDir, YDir, ZDir, Red, Green, Blue, Scale
GET TERRAIN GROUND HEIGHT (Terrain ID, X, Z)
GET TERRAIN X SIZE (Terrain ID)
GET TERRAIN Z SIZE (Terrain ID)