The only way to control which layers/geocoding services are available for the search widget in the Map Viewer is on the web map's item page settings. If you are setting up your web map in the Map Viewer, you have to save, go to the item page, set the search settings, then refresh the Map Viewer. It would be much easier if there was a way to save the search settings directly from the Map Viewer. This could either be an option under the Map Properties panel in the Map Viewer or an option to set in the layer properties or both.
