Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Absorption Filter
SSSSHADER_GRADIENTParameter: Strength
SSSSHADER_STRENGTHParameter: Filter Length
SSSSHADER_COLORDENSITYParameter: Absorption
SSSSHADER_DENSITYParameter: Samples
SSSSHADER_SAMPLESParameter: Minimum Thickness
SSSSHADER_MINTHICKNESSParameter: Scattering Length
SSSSHADER_SCATTERINGLENGTHParameter: Use Normals
SSSSHADER_USE_NORMALS