Lookup for FHIR R4B Extension for use in FHIR R4

Source ElementUsageTarget
Extension.idUseElementSameNameExtension.id
Extension.extensionUseElementSameNameExtension.extension
Extension.urlUseElementSameNameExtension.url
Extension.value[x]UseExtensionhttp://hl7.org/fhir/4.3/StructureDefinition/extension-Extension.value