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

entity.ticket_type.add_form:
  route_name: 'entity.ticket_type.add_form'
  title: 'Add Ticket type'
  appears_on:
    - entity.ticket_type.collection

entity.registration_type.add_form:
  route_name: 'entity.registration_type.add_form'
  title: 'Add Registration type'
  appears_on:
    - entity.registration_type.collection