storybook/docs/_snippets/storybook-preview-enable-toc.md

export default {
  parameters: {
    docs: {
      toc: true, // 👈 Enables the table of contents
    },
  },
};

// Replace your-framework with the framework you are using (e.g., react, vue3)
import { Preview } from '@storybook/your-framework';

const preview: Preview = {
  parameters: {
    docs: {
      toc: true, // 👈 Enables the table of contents
    },
  },
};

export default preview;