og_sm-8.x-1.0/og_sm_admin_menu/og_sm_admin_menu.routing.yml

og_sm.site.structure:
  path: '/group/{entity_type_id}/{node}/admin/structure'
  defaults:
    _controller: '\Drupal\og_sm_admin_menu\Controller\SiteAdminController::siteAdminMenuBlockPage'
    _title_callback: '\Drupal\og_sm_admin_menu\Controller\SiteAdminController::siteAdminMenuTitle'
    _title_arguments:
      title: 'Administer @site_title structure'
  requirements:
    _site_permission: 'administer site'
  options:
    _admin_route: TRUE
    parameters:
      node:
        type: og_sm:site