The only way that the Admin Console will show you a "New" button on the servers panel is if you have the WebSphere ND version installed, and the console you are looking at is connected to the Deployment Manager instance. This restriction is the same for both versions 5 and 6 of WebSphere.
If you have a Rational Application Developer or Rational Software Architect license, the
test environment you get is WebSphere Base, not WebSphere ND, so you don't get the capability of multiple servers networked together.
You can create more than one
profile, allowing you to have different environments with options set differently, but the server for each profile will still be named server1.