Updating graphic in ArcGIS JS 4.x GraphicsLayer
Esri still don't have a clue on how to modify a graphic in GraphicsLayer directly at version 4.8. You still need to clone the graphic, remove the existing one, and add the new one to realize the modification. Ref: https://developers.arcgis.com/javascript/latest/guide/functionality-matrix/index.html#graphicslayer Stone age API.