Hi Erika
Trough experimentation, I finally learned that a subform is bound to a subrecord and if not needed anymore, the subfield should be deleted in the Field Manager and not directly on the main form in order to remove everything.
As for the Natural linking, here is what I did:
Created one Application (SergeDB_Nat) and 2 databases (Orders and Clients) each database having a single main form. Orders has a single LE: Client_Id. Clients has 6 LE: Client_Id, Client_Name, Client.Addr, Client_City, Client_Pc and Client_Contact.
Used Natural linking through a subform on the Orders database main form. The choice for step 3 of Subform Settings is "Make Natural Child Records." The other choice "Show existing Natural Child Record" is not available. There are no "Pre-existing relationship" as discussed on page 141 of the User Guide.
I then did a "Hierarchical import" in the database Orders. Records appears as they should in both databases. So far so good.
When I add a record to the database Orders using Order_Form in Sesame Manager and fill in Client_Id, the details (all the 6 field values) from the corresponding Clients database (same Client_Id) do not fill the Subform on Order_Form. If I do the samething with an identical Application but using Relational Linking, and importing the data separately in each database, the corresponding details in the Clients database fields populate the subform on the Orders_Form automaticaly (as long as Clien_Id has a matching record in Clients).
I can send you the naturally linked App if what I describe here does not appear to be normal behaviour or if I misunderstand something.
TIA

Serge