gcommerce-8.x-1.0-beta5/modules/gcommerce_invoice/gcommerce_invoice.links.action.yml

group_relationship.group_invoice_add_page:
  route_name: 'entity.group_relationship.group_invoice_add_page'
  title: 'Add existing invoice'
  appears_on:
    - 'view.group_invoices.page_1'

group_relationship.group_invoice_create_page:
  route_name: 'entity.group_relationship.group_invoice_create_page'
  title: 'Add new invoice'
  appears_on:
    - 'view.group_invoices.page_1'