Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Mode
MDATA_MWS_EDGEMODE
Parameter: Add to Selection
MDATA_MWS_ADD_TO_SEL
Parameter: Tag Name
MWS_TAG_LINK
Parameter: Auto Set Selection
MWS_TAG_AUTO_SET_SEL
Parameter: Set Selection
MWS_TAG_SET_SEL
Parameter: Add Selection
MWS_TAG_ADD_SEL
Parameter: Subtract Selection
MWS_TAG_REM_SEL