I agree Edinburgh -Gatwick should have a place in the Gatwick schedule. In 2019 BA were carrying at least 350000 annually on that route.
I know times have changed, but there must still be some demand.
In my non expert view I believe Gatwick to Edinburgh could still support a twice daily (Morning and evening) BA service along with Glasgow. Perhaps as
Euroflyer becomes more established with a larger fleet and demand returns, there maybe some domestic route expansion.