Lookup for FHIR R4 Extension for use in FHIR R4B

Source ElementUsageTarget
Extension.idUseElementSameNameExtension.id
Extension.extensionUseElementSameNameExtension.extension
Extension.urlUseElementSameNameExtension.url
Extension.value[x]UseExtensionhttp://hl7.org/fhir/4.0/StructureDefinition/extension-Extension.value