compose-8.x-1.x-dev/compose.routing.yml

compose.entity_preview_controller_render:
  path: '/compose/preview/{form_build_id}/{field_name}/{delta}/{entity_type}/{entity_id}'
  defaults:
    _controller: '\Drupal\compose\Controller\EntityPreviewController::render'
    entity_id: '0'
  requirements:
    _entity_access_check: '{form_build_id, field_name, delta, entity_type, entity_id}'