Orton Filter

Knob is called a binding Object.
It can bind to any other object and control one of its value.

After connecting the binding object to the out socket of Blur (If you drop the Knob on the right side of the Blur, it will connect it automatically) the Knob will choose the most appropriate value for binding - the Blur Radius.

Now you can change the value of the Blur radius directly on the canvas.