Currently, contingent values can only be authored in ArcGIS Pro. Once a feature service is published to ArcGIS Online, then the contingent values can be configured in Field Maps Designer. If they weren't part of the original feature service, then they are not able to be configured
Also, if you create a form in Survey123 Connect that contains filtered lists that act like contingent values, this is not honoured in ArcGIS Online/Field Maps Designer. This results in the form behaving like contingent values, but the same feature service then added to a smart form via Field Maps Designer does not - you get all values in each field.
IDEA: When publishing a new form from Survey123 Connect that contains filtered lists (contingent values), store those as true contingent values and not just filtered lists. Likewise, enable the creation of contingent values in Field Maps Designer so that feature services can be modified without needing to be republished.
