entity.{{ entity_name }}.add_form:
{# Note: a content entity with bundles will add via a dedicated controller. #}
{% if not bundle_entity_type %}
  route_name: entity.{{ entity_name }}.add_form
{% else %}
  route_name: entity.{{ entity_name }}.add_page
{% endif %}
  title: 'Add {{ label }}'
  appears_on:
    - entity.{{ entity_name }}.collection