Hi Davide, try this:
Manual mapping
It's always possible to manually define the mapping for new elements in the Data Model. After the creation of a new element we can define, element by element, the mapping. This is done with the mapping properties of the element selected. For every new element (Entity, Attribute, Relation) we can choose the linked Database element from the Database Metadata (retrieved with the "Refresh" functionality).
After the creation of the "Customer" entity, the Mapping properties are empty:
For the Entity and for every attribute we manually define the mapping:
Let me know if it worked!