Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Update
POLYGONSELECTIONTAG_UPDATE
Parameter: Select&$Shift to add
Ctrl to remove from selection
POLYGONSELECTIONTAG_COMMAND1
Parameter: Deselect
POLYGONSELECTIONTAG_COMMAND4
Parameter: Hide
POLYGONSELECTIONTAG_COMMAND5
Parameter: Show
POLYGONSELECTIONTAG_COMMAND6
Parameter: Solo
POLYGONSELECTIONTAG_COMMAND2
Parameter: Show All
POLYGONSELECTIONTAG_UNHIDEALL
Parameter: Use Fields
POLYGONSELECTIONTAG_ENABLEFIELDS
Parameter: Tolerance
POLYGONSELECTIONTAG_FIELDTOLERANCE
Parameter: Use Deformed Points
POLYGONSELECTIONTAG_DEFORMEDSTATE
Parameter: Fields
POLYGONSELECTIONTAG_FIELDS