As Survey123 writes data to an ArcGIS feature service, there are some limitations imposed by feature service capabilities. One of these is a limitation of one geometry field per layer/table. This normally leads to a limitation of one point per form. This can be worked around through a couple of methods:
- Adding a repeat to the form. Repeats get stored in their own tables and also support up to 1 geometry per repeat section
- Using the esriFieldType of null to display a second (and third, etc.) point, which is not written to the feature service. The additional points can be referenced by other fields to, for example, store the Lat/Lon of the point as numeric data in the table. See https://community.esri.com/groups/survey123/blog/2017/10/26/the-power-of-nothing for examples.