I have a survey with a geopoint question that I want to use our custom geocoder for, so it just shows local addresses rather than all over the world. A couple of references explain how to do this with the geopoint question type:
Geopoints—ArcGIS Survey123 | Documentation
To set a specific locator to return results from, supply the locator's item ID in the bind::esri:parameters column, for example, geocode=36ff9e8c13e042a58cfce4ad87f55d19
also
Survey123 Tricks of the Trade: Addresses, and the XLSForm geocode appearance
Additionally, you can also use the bind::esri:parameters column of your XLSForm to specify the item ID of the ArcGIS locator service or locator view to be used. If you do this, the organization’s geocoding service configuration will be ignored, and the specified locator service will be used instead.
The screenshot below shows how to use the geocode bind::esri:parameter to work with a specific locator service.

In the same survey I am using a pulldata on the same geocoder, to do a reverse geocode...
pulldata("@geopoint",${gpslocation},"reversegeocode.address.Address","https://www.portlandmaps.com/arcgis/rest/services/Public/Geocoding_PDX/GeocodeServer/reverseGeocode","distance=100","outSR=4326")
This custom geocoder does not have an item ID, so how do I set the geocoder in the geopoint to use the URL?