htools-8.x-1.x-dev/modules/htools_relations/htools_relations.links.action.yml

entity.relational_entity.add_form:
  route_name: entity.relational_entity.add_page
  title: 'Add Relational entity'
  appears_on:
    - entity.relational_entity.collection
entity.relational_entity_type.add_form:
  route_name: entity.relational_entity_type.add_form
  title: 'Add Relational entity type'
  appears_on:
    - entity.relational_entity_type.collection