I'm trying to do this in Odoo 16 online, I keep getting this error when trying to create a new view. "Oh snap! Document is empty, line 1, column 1" 

I've double check everything is filled out like the screenshot. Can someone help?

Base your work on this Proof of Concept.

UPDATE: Code in the GIST now supports Odoo 15 and Odoo 16

Given two Companies, USA with ID=1 and CANADA with ID=2, you can achieve this:

Via a Custom View:

Using this code:

https://gist.github.com/ray-odoo/17a1dc72c7f59314ed1592b1a3db7e0c