Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Absorption Filter
SSSSHADER_GRADIENT
Parameter: Strength
SSSSHADER_STRENGTH
Parameter: Filter Length
SSSSHADER_COLORDENSITY
Parameter: Absorption
SSSSHADER_DENSITY
Parameter: Samples
SSSSHADER_SAMPLES
Parameter: Minimum Thickness
SSSSHADER_MINTHICKNESS
Parameter: Scattering Length
SSSSHADER_SCATTERINGLENGTH
Parameter: Use Normals
SSSSHADER_USE_NORMALS