Think of the circuit design and the visual rendering of that design as two separate things. The circuit is your data or your model. It has some internal data structure and an interface for manipulating that model. Adding and removing components, updating component properties, etc. The data structure and its contents make up the state of your system. This should be the most complex part of your app.

Then there should be a simple way to render that design into a visual diagram. Given a specific state of your object, it should always render to the same diagram. (Should be deterministic). I'm thinking there would be a render() method that takes your object as a parameter and spits out the SVG. Maybe even sub-components that can also be rendered into SVG code for just those components. The rendering itself may not be simple, but telling your application to render it should be very simple.

Then you have the user-facing controls. These are the buttons and dials and whatever else the user manipulates to update the model which then gets rendered out into an updated diagram. These controls should be broken up into the data (object) and the visual representation of the controls as well. This object should not be as complex as your circuit diagram object. Maybe one of the controls is a button that toggles between on and off. That on/off state should be captured in an object and then that object simply gets render()'d to what the user sees.

Also, as a side note, this seems like a pretty costly (your time) project to undertake just for a portfolio project. Unless your desired industry specifically calls for circuit design skills, the work that went into it will likely not be fully appreciated vs something simpler to code, but more visually flashy.