The Dynamics 365 Lead qualification process creates a Contact with values from the Lead, and the original Lead becomes read-only.
The S4D Save To Dynamics Submit Action automatically recognizes when an existing Lead has been converted, and attempts to update the same fields on the Contact instead. Note:
If a field of the same name does not exist on the Contact, it will be omitted from the update.
Dynamics 365 Marketing Lists are targeted at a single entity type, so a Contact cannot be associated with a List that targets Leads.
If you enable detailed logging you will see this in action:
21088 11:41:01 DEBUG FuseIT.S4D.WebToDynamics.SitecoreExperienceForms.SubmitActions.SaveToDynamics - GetDynamicsEntityAsync: attempting to load existing 'lead' entity matching { [emailaddress1, test@example.com] }.
6100 11:41:01 DEBUG FuseIT.S4D.WebToDynamics.Utility.ODataUtility - TransformEntityAsync: Substituting converted Lead 40e71d3e-bfc9-ec11-a7b6-0022481435ab for Contact 9d77a8ec-18cc-ec11-a7b6-0022481435ab.
6100 11:41:01 DEBUG FuseIT.S4D.WebToDynamics.SitecoreExperienceForms.SubmitActions.SaveToDynamics - UpsertDynamicsEntityAsync: omitting field 'subject' because it does not exist on entity 'contact'.
6100 11:41:01 DEBUG FuseIT.S4D.WebToDynamics.SitecoreExperienceForms.SubmitActions.SaveToDynamics - UpsertDynamicsEntityAsync: no List associations will be added as entity has changed from 'lead' to 'contact'.
6100 11:41:01 DEBUG FuseIT.S4D.WebToDynamics.SitecoreExperienceForms.SubmitActions.SaveToDynamics - UpsertDynamicsEntityAsync: found 'contact' entity { [contactid, 9d77a8ec-18cc-ec11-a7b6-0022481435ab] }, attempting update.