Are you talking about
the FPS Meter? FYI it's actually a very old tool.
It doesn't give you a realtime view, but the
FPS chart can show you your general FPS performance, without obstructing your viewport.
A good place to put the realtime FPS meter would be the new
Perf Monitor. I don't think there's currently any work on that, though.
It's not possible to move the window. The FPS Meter doesn't block interactions with stuff underneath it, though. You can still interact. But yes, I understand that it's harder because the Meter is obstructing your view.