A Calculate Field geoprocessing service configured with the geoprocessing widget in a Web AppBuilder for ArcGIS application does not write outputs to a referenced feature service.

Workaround

Use the Smart Editor widget in Web AppBuilder for ArcGIS to create an expression whenever a new feature is added. https://enterprise.arcgis.com/en/portal/latest/use/widget-smart-editor.htm

Publish a feature service with a calculation attribute rule from ArcGIS Pro. https://www.esri.com/arcgis-blog/products/product/data-management/attribute-rules-whats-new-in-arcgis-pro-2-3-and-arcgis-enterprise-10-7/

Steps to Reproduce