There is no quick undo !

[Kashumy]

can you add div button in circuit1js.html here for undo (always show)

[pfalstad]

yes, maybe there should be a toolbar. I always use Ctrl-Z (or Cmd-Z on Mac)

[TishSerg]

I always use Ctrl-Z

Me too. But it gives some undesired effect. It resets the simulation and adjusts my potentiometers (somewhy my potentiometers are adjusted the same way when I open the circuit file.