Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: UVs
OBJEXPORTOPTIONS_EXPORT_UVSParameter: Normals
OBJEXPORTOPTIONS_NORMALSParameter: Vertex Colors
OBJEXPORTOPTIONS_VERTEX_COLORParameter: Flip X Axis
OBJEXPORTOPTIONS_POINTTRANSFORM_FLIPXParameter: Swap X and Y Axes
OBJEXPORTOPTIONS_POINTTRANSFORM_SWAPXYParameter: Flip Y Axis
OBJEXPORTOPTIONS_POINTTRANSFORM_FLIPYParameter: Swap X and Z Axes
OBJEXPORTOPTIONS_POINTTRANSFORM_SWAPXZParameter: Flip Z Axis
OBJEXPORTOPTIONS_POINTTRANSFORM_FLIPZParameter: Swap Y and Z Axes
OBJEXPORTOPTIONS_POINTTRANSFORM_SWAPYZParameter: Flip Faces
OBJEXPORTOPTIONS_FLIPFACESParameter: Resolve N-gons
OBJEXPORTOPTIONS_TRIANGULATE_NGONSParameter: Objects as Groups
OBJEXPORTOPTIONS_OBJECTS_AS_GROUPSParameter: Material
OBJEXPORTOPTIONS_MATERIALParameter: Default Material
OBJEXPORTOPTIONS_DEFAULTMATERIALParameter: Invert Transparency
OBJEXPORTOPTIONS_INVERT_TRANSPARENCYParameter: Frame Range
OBJEXPORTOPTIONS_ANIMATION_TYPEParameter: Start Frame
OBJEXPORTOPTIONS_FRAME_STARTParameter: End Frame
OBJEXPORTOPTIONS_FRAME_ENDParameter: Frame Step
OBJEXPORTOPTIONS_FRAME_STEPParameter: Shared Material File
OBJEXPORTOPTIONS_SHARED_MTL_FILEParameter: Export as UTF-8
OBJEXPORTOPTIONS_ENCODING_UTF8