autonomic-block-theme/js/block-styles.js

wp.domReady( () => {
  wp.blocks.registerBlockStyle(
    'core/heading', {
      name: 'tabbed-heading',
      label: 'Tabbed Heading',
    }
  )

  wp.blocks.registerBlockStyle(
    'core/post-title', {
      name: 'tabbed-heading',
      label: 'Tabbed Heading',
    }
  )
} )