Netlify CMS text widget where user may toggle between 'string' and 'text' widget controls.

another-text-widget.js

import CMS from "netlify-cms-app";
import { createElement, useState } from "react";

const widget = {
  control: BetterTextWidgetControl,
  name: "betterTextWidget",
  preview: BetterTextWidgetPreview,
};
export default widget;

const newlineRegExp = /\n/;

function BetterTextWidgetControl(props) {
  const { classNameWrapper, value } = props;
  const [multilineEnabled, setMultilineEnabled] = useState(
    newlineRegExp.test(value)
  );
  const controlWidget = CMS.getWidget(
    multilineEnabled === true ? "text" : "string"
  );
  return (
    <form
      className={classNameWrapper}
      onSubmit={(event) => {
        event.preventDefault();
      }}
    >
      <label>
        Multi-line Enabled
        <input
          checked={multilineEnabled}
          onChange={(event) => {
            setMultilineEnabled((toggle) => !toggle);
          }}
          name="multilineEnabled"
          type="checkbox"
        />
      </label>
      {createElement(controlWidget.control, props)}
    </form>
  );
}

function BetterTextWidgetPreview({ value }) {
  return value;
}