For example add buttons and sliders that show on screen and can be used to effect change in a circuit. Sliders can vary the voltage output or frequency of a source, buttons can be used to toggle things like switches, etc.

This could allow for some really cool circuits and would provide an analogue to real world push buttons and sliders/rotary dials.

The only issue I see with this would be determining whether the user is try to push the button or select it, perhaps make them so that they can only be selected by selection box?