Hello,
When there's a parent missing to a child, the Default button becomes visible.
But if there are no errors, you won't see the button.
It would be ideal if the Default button would be visible at all times, or maybe have an overview window (like the Normalize window), where you could set up the default mapping.
In the attached post below, there's a workaround, but it would be less time consuming to just use the Default button.
When updating the entities, we use a combination of Smart Import, Data Readers and Entity Editor.
It will also be easier to make changes and handover responsibility to the customer.