code before <KnobComposed>

pushbutton.xml

<PushButton>
  <Size>20f,20f</Size>
  <NumberStates>2</NumberStates>
  <State>
    <Number>0</Number>
    <Text>D</Text>
  </State>
  <State>
    <Number>1</Number>
    <Text>E</Text>
  </State>
  <Connection>
    <EmitOnPressAndRelease>true</EmitOnPressAndRelease>
    <ConfigKey>[EffectRack<Variable name="EffectRack"/>_EffectUnit<Variable name="EffectUnit"/>_Effect<Variable name="Effect"/>],button_parameter<Variable name="EffectParameter"/></ConfigKey>
  </Connection>
</PushButton>

I have inserted this code just before , here https://github.com/mixxxdj/developer_skins/blob/master/Deere/effect_parameter_knob.xml#L15