Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Scale
FORGERIO_SCALE_FACTOR_IMPORT
Parameter: UVs
FORGERIO_IMPORT_UVW
Parameter: Vertex Colors
FORGERIO_IMPORT_POLYPAINT
Parameter: Polygon Groups
FORGERIO_IMPORT_POLYGROUP
Parameter: Materials
FORGERIO_IMPORT_MATERIALS
Parameter: Replace Existing
FORGERIO_IMPORT_REPLACE_EXISTING