Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Knife
MDATA_BRUSHMODIFIERBASE_ENABLED
Parameter: Strength
MDATA_BRUSHMODIFIERBASE_STRENGTH
Parameter: Invert
BM_KNIFE_INVERT
Parameter: Pinch
BM_KNIFE_PINCH
Parameter: Push
BM_KNIFE_PUSH