Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Keep Bridge Open
USDIMPORTER_KEEPBRIDGEOPENParameter: Cameras
USDIMPORTER_CAMERASParameter: Instances
USDIMPORTER_INSTANCESParameter: Lights
USDIMPORTER_LIGHTUNITSParameter: Geometry
USDIMPORTER_GEOMETRYParameter: Normals
USDIMPORTER_NORMALSParameter: Phong Angle
USDIMPORTER_PHONG_ANGLEParameter: UVs
USDIMPORTER_UVParameter: Display Color
USDIMPORTER_DISPLAYCOLORParameter: Materials
USDIMPORTER_MATERIALS