Relating model based on external data source to Salesforce object

If I create an external data source model that has accounts. Each account has a number as its identifier. I also have an object in Salesforce that has these same accounts with the same numbers. This is to store additional details about the accounts that isn’t allowed by the external data source. How would I relate them so I could display data from both the external data source and from my Salesforce object on the same table?

A series of custom field renderers could be used. Easy if it’s read only. For editing it would be easiest to go to popup from row action. Otherwise Table w/ inline edit would be more complex for the snippet.