Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Preset
XMBSUBSURFACESHADER_PRESETParameter: Color
XMBSUBSURFACESHADER_DIFFUSEParameter: Strength
XMBSUBSURFACESHADER_STRENGTHParameter: Shader
XMBSUBSURFACESHADER_SHADERParameter: Path Length
XMBSUBSURFACESHADER_LENGTHParameter: Red
XMBSUBSURFACESHADER_LENGTH_RParameter: Green
XMBSUBSURFACESHADER_LENGTH_GParameter: Blue
XMBSUBSURFACESHADER_LENGTH_BParameter: Mode
XMBSUBSURFACESHADER_MULTIPLE_MODEParameter: Enabled
XMBSUBSURFACESHADER_MULTIPLE_ENABLEDParameter: Fast Evaluation
XMBSUBSURFACESHADER_CACHE_INTERPOLATIONParameter: Sample Density
XMBSUBSURFACESHADER_CACHE_SAMPLE_DENSITYParameter: Smoothing
XMBSUBSURFACESHADER_CACHE_SMOOTHINGParameter: Threshold
XMBSUBSURFACESHADER_CACHE_ERRORParameter: Separate Color Channels
XMBSUBSURFACESHADER_DIRECT_SPLITParameter: Minimum Threshold
XMBSUBSURFACESHADER_DIRECT_RATIOParameter: Custom Sampling
XMBSUBSURFACESHADER_MULTIPLE_CUSTOM_ENABLEDParameter: Sampling Subdivision
XMBSUBSURFACESHADER_MULTIPLE_CUSTOM_SAMPLINGParameter: Enabled
XMBSUBSURFACESHADER_SINGLE_ENABLEDParameter: Separate Color Channels
XMBSUBSURFACESHADER_SINGLE_SPLITParameter: Trace Shadow Rays
XMBSUBSURFACESHADER_SINGLE_TRACEParameter: Phase Function
XMBSUBSURFACESHADER_SINGLE_PHASEParameter: Custom Sampling
XMBSUBSURFACESHADER_SINGLE_CUSTOM_ENABLEDParameter: Sampling Subdivision
XMBSUBSURFACESHADER_SINGLE_CUSTOM_SAMPLINGParameter: Fresnel Reflectivity
XMBSUBSURFACESHADER_FRESNELParameter: Dithering
XMBSUBSURFACESHADER_DITHERParameter: Index of Refraction
XMBSUBSURFACESHADER_IORParameter: Compute GI Contribution
XMBSUBSURFACESHADER_LIGHTS_GIParameter: Use Lights
XMBSUBSURFACESHADER_LIGHTS_MODEParameter: Lights
XMBSUBSURFACESHADER_LIGHTS