Updated Drupal to 8.6. This goes with the following updates because it's possible...

[yaffs-website] / web / core / modules / config / tests / config_test / config_test.links.action.yml

config_test_entity_add_local_action:
  route_name: config_test.entity_add
  title: 'Add test configuration'
  appears_on:
    - entity.config_test.collection