While doing migration for corporate website and while migrating jcr configuration to yaml we had couple of multivalue fields defined like on attachment 1.png. The point is in categoriesFilter/field it was working without 'name' or 'label' property but after doing 'Download as YAML' and using this yaml definition dialog is not working. Technically dialog opens but without actions buttons and any dialog tab including and nexts after this multivalue field. And with error in log http://pastebin.com/NgJRhBzR

This is how field looks like after "Download as YAML":

        - name: categoriesFilter
          description:
          label: Show filter for
          class: info.magnolia.ui.form.field.definition.MultiValueFieldDefinition
          field:
            appName: categories
            fieldEditable: false
            targetWorkspace: category
            type: String
            class: info.magnolia.ui.form.field.definition.LinkFieldDefinition
            identifierToPathConverter:
              class: info.magnolia.ui.form.field.converter.BaseIdentifierToPathConverter

and when 'name' or 'label' is added into 'field' subnode then all is ok. Unfortunately when it happens is quite tough to find what is missing. Some better error message or not requiring this name will be cool.

BTW also documentation page https://documentation.magnolia-cms.com/display/DOCS/Multivalue+field#4dffdc6543cd4946b9e2d75165a6cef0 is using examples of jcr definition withotu name or label and then yaml with name...