How to display invoice amount in functional currency on invoice page

Summary

Display invoice amount in functional currency

Content

Functional currency is USD.  We enter an invoice in GBP so the amount is in GBP.  The exchange rate and inverse exchange rate fields are populated with the corporate exchange rate.  But there is no field on the invoice that will display invoice in functional currency. 

Also, the amount in functional currency is not a field on the Search Results screen.  We also want to search, sort, or filter by amount in functional currency.  

Version

20C