The label.xml will updated with the required field. When it goes to rendering the element, the template should have an option not check the xsd schema. So there is an ongoing change for that in Geonetwork main branch https://github.com/geonetwork/core-geonetwork/pull/8294
As the discussion from https://github.com/metadata101/iso19139.ca.HNAP/issues/315
The label.xml will updated with the required field. When it goes to rendering the element, the template should have an option not check the xsd schema. So there is an ongoing change for that in Geonetwork main branch https://github.com/geonetwork/core-geonetwork/pull/8294