storybook-theme-css-vars/dist/esm/preset/manager.js

Theme switcher tool addon that changes the theme using CSS custom properties

import { addons, types } from "@storybook/addons";
import { ADDON_ID, TOOL_ID } from "../constants";
import { ThemeSwitcher } from "../theme/ThemeSwitcher";
addons.register(ADDON_ID, function () {
  addons.add(TOOL_ID, {
    type: types.TOOL,
    title: "Theme switcher",
    match: function match(_ref) {
      var viewMode = _ref.viewMode;
      return !!(viewMode && viewMode.match(/^(story|docs)$/));
    },
    render: ThemeSwitcher
  });
});