component.js

...
import { Button } from '@storybook/angular/demo';

storiesOf('Addon|Notes', module)
  .add(
    'Simple note',
    withNotes({ text: 'My notes on some button' })(() => ({
      component: Button,
      props: {
        text: 'Notes on some Button',
        onClick: () => {},
      },
    }))
  )