Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Variable Tag
FIELDLAYER_WEIGHT_LINKParameter: Mode
FIELDLAYER_WEIGHT_MODEParameter: Radius
FIELDLAYER_WEIGHT_RADIUSParameter: Distance Falloff
FIELDLAYER_WEIGHT_DISTANCEFALLOFFParameter: Use Deformed Points
FIELDLAYER_WEIGHT_USEDEFORMEDParameter: Constant Update
FIELDLAYER_WEIGHT_CONSTANTUPDATE