I am having this same issue George. Were you able to find a fix?

Hi,

You can inherit the corresponding model, and add the necessary fields into it. If you are using Odoo enterprise and access to Odoo studio, you can easily drag and add fields to the model.

If you are using the Odoo community edition, same can be achieved by a custom module or customizing from the user interface.

For more please read the official documentation: https://www.odoo.com/documentation/15.0/developer/howtos/rdtraining/13_inheritance.html

Thanks & Regards