Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Splitting
OBJIMPORTOPTIONS_SPLITBYParameter: Lines
OBJIMPORTOPTIONS_LINESParameter: UVs
OBJIMPORTOPTIONS_IMPORT_UVSParameter: Normals
OBJIMPORTOPTIONS_NORMALSParameter: Phong Angle
OBJIMPORTOPTIONS_PHONG_ANGLE_DEFAULTParameter: Vertex Colors
OBJIMPORTOPTIONS_VERTEX_COLORParameter: Flip X Axis
OBJIMPORTOPTIONS_POINTTRANSFORM_FLIPXParameter: Swap X and Y Axes
OBJIMPORTOPTIONS_POINTTRANSFORM_SWAPXYParameter: Flip Y Axis
OBJIMPORTOPTIONS_POINTTRANSFORM_FLIPYParameter: Swap X and Z Axes
OBJIMPORTOPTIONS_POINTTRANSFORM_SWAPXZParameter: Flip Z Axis
OBJIMPORTOPTIONS_POINTTRANSFORM_FLIPZParameter: Swap Y and Z Axes
OBJIMPORTOPTIONS_POINTTRANSFORM_SWAPYZParameter: Flip Faces
OBJIMPORTOPTIONS_FLIPFACESParameter: Material
OBJIMPORTOPTIONS_MATERIALParameter: Default Material
OBJIMPORTOPTIONS_DEFAULTMATERIALParameter: Material Mix Mode
OBJIMPORTOPTIONS_MATERIAL_MIXMODEParameter: Invert Transparency
OBJIMPORTOPTIONS_INVERT_TRANSPARENCYParameter: Sequence
OBJIMPORTOPTIONS_SEQUENCE_ANIMATIONParameter: FPS
OBJIMPORTOPTIONS_SEQUENCE_FPSParameter: Frame Step
OBJIMPORTOPTIONS_SEQUENCE_FRAME_STEPParameter: Shared Material
OBJIMPORTOPTIONS_SEQUENCE_SHARED_MATERIALParameter: PLA Interpolation
OBJIMPORTOPTIONS_SEQUENCE_PLAParameter: Script Console Reporting
OBJIMPORTOPTIONS_REPORT_SCRIPTCONSOLEParameter: Import as UTF-8
OBJIMPORTOPTIONS_ENCODING_UTF8