In Modeler, when creating a new Schema, it is possible to use the mode Import to define the content of the schema using an XSD resource. This XSD resource is editable in Modeler or via Git access, so it's possible to add/remove fields in the schema definition. But when going back to the schema created previously using the resource, the content is not updated and is still the original one defined at creation.
A solution could be adding a refresh button to update the list of fields imported from the XSD.