Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Target
PREF_IMEXPORT_NODESPACEParameter: Show Dialog
PREF_IMEXPORT_SHOW_IMPORT_DLGParameter: Merge on Drag & Drop
PREF_IMEXPORT_MERGE_ON_DDParameter: Show Dialog
PREF_IMEXPORT_SHOW_EXPORT_DLGParameter: PREF_IMEXPORT_INFOTEXT
PREF_IMEXPORT_INFOTEXT