Maybe the OP can clarify what they are trying to achieve?
Whatever program I have used the render process locks the program whether it is in a tab or ‘New window’. As ps1borg says, undocking the render tab to floating gives you what all the other programs look like, a floating window with the renderer in it. Render queue would be the way to go to if you are trying to free up the program if renders are interrupting your workflow.
Or am I missing a fundamental here?