Using the following link, you will see how to connect to a console session (or now called „admin session“) using a saved .rdp file with rdp client version 6.1

RDP 6.1 Client Änderungen connect to console:i:1 wird zu administrative session:i:1

It says, if you used to following in your old rdp-files
connect to console:i:1

you should use the following from now on with version 6.1:
administrative session:i:1