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: Geometry
USDIMPORTER_GEOMETRYParameter: Materials
USDIMPORTER_MATERIALSParameter: Instances
USDIMPORTER_INSTANCESParameter: Lights
USDIMPORTER_LIGHTUNITSParameter: Normals
USDIMPORTER_GEOMETRY_NORMALSParameter: Phong Angle
USDIMPORTER_GEOMETRY_PHONG_ANGLEParameter: UVs
USDIMPORTER_GEOMETRY_UVParameter: Display Color
USDIMPORTER_GEOMETRY_DISPLAYCOLORParameter: Tracks
USDIMPORTER_ANIMATION_TRSParameter: Clean Tracks
USDIMPORTER_ANIMATION_CLEANTRACKSParameter: Skin
USDIMPORTER_ANIMATION_SKELETAL