tmgmt-8.x-1.x-dev/sources/content/tmgmt_content.routing.yml

tmgmt_content.job_item_preview:
  path: '/tmgmt/content/preview/{tmgmt_job_item}/{view_mode}'
  defaults:
    _controller: '\Drupal\tmgmt_content\Controller\ContentTranslationPreviewController::preview'
    _title_callback: '\Drupal\tmgmt_content\Controller\ContentTranslationPreviewController::title'
    view_mode: 'full'
  requirements:
    _key_access_check: 'TRUE'