Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Clear
MGSELECTIONTAG_CLEARParameter: Invert
MGSELECTIONTAG_INVERTParameter: Display Indices
MGSELECTIONTAG_NUMBERSParameter: Use Fields
MGSELECTIONTAG_USEFIELDSParameter: Tolerance
MGSELECTIONTAG_FIELDTOLERANCEParameter: Use Deformed Points
MGSELECTIONTAG_FIELDDEFORMParameter: Fields
MGSELECTIONTAG_FIELDS