Enable

<input id="slider" style="width: 300px" />
<script>
  $("#slider").kendoSlider({
    precision: 4,
    smallStep:0.0001,
    largeStep:0.0001,
    min:0,
    max:0.0004,
    value: 0.0002,
    tooltip: {
      format: "{0:#,#.####}"
    }
  });
  
// get a reference to the slider widget
var slider = $("#slider").data("kendoSlider");

// disables the slider
slider.enable(false);

// enables the slider
slider.enable(true);

</script>