Why system not allowing cross country tax registration numbers to save in Global configurator owner

Why system not allowing cross country tax registration numbers to save in Global configurator owner setup?

Ex:- I have a business across Europe but tax reported only to UK in this situation I should define UK Tax regime and Tax code and this must allow to keep other country registration numbers because these registration numbers are external parties like Suppliers and Customers so we just need them for reporting but present architecture not allow to save Belgium registration numbers while creating a customer or supplier in UK tax regime

This must be addressed in simple way instead of making it complex it would have given a Tax registration mapping lookup code to avoid long definitions by country specific Tax definitions