bar or a thumb of a slider, to being a controller
    // that the user can drag to change the value of the instrument.
    // This assumes that the scale (a "Graduated" Panel) is named "SCALE".
    // The alwaysVisible parameter determines whether the object's visibility
    // is controlled by the "SCALE"'s Panel.isEnabled property.
    function sliderActions(alwaysVisible) {
      return {
        isActionable: true,
        actionDown: (e, obj) => {
          obj._dragging = true;
          obj._original