What? No. Sometimes I want more than one of the same window open. Have you heard of alt-tab?
I'm not saying this to be snarky, I'm genuinely curious - Why?
A lot of people seem to have asked for multi-windows as a QoL feature, and want to keep it. It sounds like you have some uses in mind for two windows of a kind, and people have mentioned drag-and-drop. But I don't know what you'd use it for, or what you'd be dragging and dropping. Can someone explain it, so I might use it?
I will often want to monitor something over time on a particular tab of the Economics window.
I love having the ability now to open a new Econ window to address other things that occur while I am monitoring the first thing.
For example, say I want to switch a colony's population status to "Stable" as soon as it has reached a specific population.
Maybe it will take many months for the population to reach that target.
In VB6, since I could only have one Econ window, I just had to remember about this particular task as I respond to all the other things that need attention.
New ship built: go to Shipyard tab and queue new ones.
Build queue finishes: go to Industry tab and queue more.
Research finishes: go to Research tab and start next project.
Etc., etc., etc.
And all the time, I have to keep in the back of my mind this one thing I'm keeping an eye on, and go back and check the population of this colony every little while.
But now I can keep an Econ window open showing that specific colony summary screen.
I can attend to all the other necessary things in another window, and not disturb my "don't forget this" window.
In fact, I keep a small stack of Econ windows open in a specific place for things like this.
I think of it as my "string around the finger" list.