cms_content_sync-3.0.x-dev/modules/cms_content_sync_private_environment/cms_content_sync_private_environment.links.menu.yml

cms_content_sync_private_environment.private_environment:
  title: 'Private Environment'
  route_name: cms_content_sync_private_environment.private_environment
  parent: cms_content_sync.main
  description: 'Content Sync - Private Environment'
  weight: 10