It sounds like your existing fields accepts 'open text' entry.
select_one questions in Survey123 leverage:
- Choice Lists (also known as domain values/descriptions); or
- An external csv file
When publishing a new survey, Survey123 will create an attribute list in your Hosted Feature Layer for each select_one list.
When targeting an existing survey, Survey123 will identify if the field is open or if it has a list.
Survey123 does NOT create a selection from existing values. Only if there's a list.
So you will need to:
- Manually create a list of values for the field; or
- Create an external csv of choice lists to constrain the input values at a Survey. The Hosted Feature Layer will accept any response (e.g. if populated through Field Maps).
https://doc.arcgis.com/en/arcgis-online/manage-data/define-attribute-lists-and-ranges.htm
However, I'm a bit skeptical that this is what you need. Creating sequential sub records for existing records? Looking them up with a select_one question? It sounds like you're relatively new to Survey123 and looking to undertake a relatively advanced workflow. You may need to create a related table (the repeat) in your feature service. You'll also want to explore the globalid/parentglobalid relationship between features. If you post more about what you're trying to achieve and the existing data model, we may be able to provide some good resources to help.
