I was able to get gpt4 to do a lot of useful work. But for some reason it completely falls apart for this scenario. May be because it has to think in second order to achieve the task. Perhaps you could take a crack at this:

Prerequisite (for you the human)> You have a file at src/SampleReactComponent.jsx that has below simple react component: const SampleReactComponent = (props) => {

    const [var1, setVar1] = React.useState(false);
    const [var2, setVar2] = React.useState(false);
    const [var3, setVar3] = React.useState(false);

return (<></>); };

export default SampleReactComponent;

********** Prompt for GPT4: I'm at my project root working on a reactjs project. Update the component in src/SampleReactComponent.jsx file by adding a new const variable after the existing variables. You cannot use cat command as the file is too big. You can use grep with necessary flags and sed to achieve the task. I'll provide you the output of each command that you generate. *************

That's it. It would do any complex modification on fully provided data (included in the prompt) but something like above where it has to build a model from secondary prompts will totally fall apart.