SQL Server data source does not support named instances

I have SQL Server Express and Grafana both installed on my local machine. The SQL server is accessible via “localhost\SqlExpress”. SQL Server Browser service is running.
When I use “Localhost\SqlExpress” in the “Host” field of the SQL Server data source, I get this error message “No instance matching ‘SQLEXPRESS’ returned from host ‘localhost’”.

Seems that SQL Server data source does not accept named instances and only relies on IP/Host! Is there a workaround for this?