How to have 2 connections, same server, different user?

While the main pgadmin console lets me define multiple connections to
the same server in different roles, the SQL query window will not let me
select them.  Once I've selected a connection as a specific role (say,
postgres:5488), then I cannot ever select a differently-roled connection
as a different user (say, db_admin:5488) to the same database.

I think this is probably simply a deficiency in the connection selector
in the SQL window, which only displays IP:Port instead of the list of
named connections available in the main console.

Can anyone suggest a workaround?

--Josh Berkus