How to export/import Tax registration numbers for Vendors

 D365FO contains a special data entity which can be used for both DMF export/import and also in Excel Add-in, but... 

There is an interesting InnerJoin inside of this data entity, which may be a hurdle for understanding why you still have no records exported; nevertheless, you have some in TaxRegistration table.

In fact, when you create records in Vendor Registration IDs form, it does not tell you about this constraint.

To get these records exported, you simply need to add it in Registration categories.

and voila!