Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Scale
FORGERIO_SCALE_FACTOR_EXPORT
Parameter: UVs
FORGERIO_EXPORT_UVW
Parameter: Vertex Colors
FORGERIO_EXPORT_POLYPAINT
Parameter: Polygon Groups
FORGERIO_EXPORT_POLYGROUP
Parameter: Connect With Children
FORGERIO_EXPORT_CONNECTWITHCHILDREN
Parameter: Materials
FORGERIO_EXPORT_MATERIALS
Parameter: FORGERIO_EXPORT_WARNING
FORGERIO_EXPORT_WARNING