Custom Form Controls - Save to Salesforce

When creating a custom Sitecore Experience Form Field that needs to be mapped to a Salesforce field in the S4S Save to Salesforce submit action, it is necessary to add the custom form field in the core database to /sitecore/client/Applications/FormsBuilder/Components/Layouts/Actions/S4SSaveToSalesforce/PageSettings/FormClientApi.

Locate the IncludedFieldTypeIds field:

Open

Add your custom field from the left side list to the Selected list at right, and save.