widget_engine-8.x-1.2/widget_engine.links.action.yml

entity.widget.add_form:
  route_name: 'entity.widget.add_page'
  title: 'Add Widget'
  appears_on:
    - entity.widget.collection
entity.widget_type.add_form:
  route_name: 'entity.widget_type.add_form'
  title: 'Add Widget type'
  appears_on:
    - entity.widget_type.collection