Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Strength
MDATA_MGWEIGHTTOOL_STRENGTH
Parameter: Mode
MDATA_MGWEIGHTTOOL_MODE
Parameter: Apply All
MDATA_MGWEIGHTTOOL_APPLYALL
Parameter: Apply Selected
MDATA_MGWEIGHTTOOL_APPLYSELECTED
Parameter: Radius
MDATA_MGWEIGHTTOOL_RADIUS
Parameter: Step
MDATA_MGWEIGHTTOOL_STEP
Parameter: Pressure
MDATA_MGWEIGHTTOOL_PRESSURE
Parameter: Show Weights
MDATA_MGWEIGHTTOOL_DISPLAY
Parameter: Visible Only
MDATA_MGWEIGHTTOOL_VISIBLE_ONLY