collection-8.x-1.x-dev/collection.links.action.yml

collection.local_actions:
  deriver: 'Drupal\collection\Plugin\Derivative\DynamicLocalActions'
entity.collection.add_form:
  route_name: entity.collection.add_page
  title: 'Add Collection'
  appears_on:
    - entity.collection.collection
entity.collection_type.add_form:
  route_name: entity.collection_type.add_form
  title: 'Add Collection type'
  appears_on:
    - entity.collection_type.collection
entity.collection_item_type.add_form:
  route_name: entity.collection_item_type.add_form
  title: 'Add Collection item type'
  appears_on:
    - entity.collection_item_type.collection