References without a unique lookup
When a reference field does not have a unique lookup it sometimes has a combination of fields that make the referenced business object unique. In this case, automatically all fields that make this business object unique will be added to the template (Excel).
Some business objects do not have a unique key at all, not from business logic and not by configuration (this could be the case for example for free business objects). In this case, no other fields than the reference field (lookup) will be available.
Example
The space lookup (code) is not unique.
When there is a space reference in the layout, next to the space.code field, automatically also the property.code and floor.code fields are added.