og_sm-8.x-1.0/og_sm_menu/og_sm_menu.links.action.yml

og_sm.site_menu.add_link:
  route_name: 'og_sm.site_menu.add_link'
  title: 'Add link'
  class: \Drupal\menu_ui\Plugin\Menu\LocalAction\MenuLinkAdd
  appears_on:
   - og_sm.site_menu