In short: The ability to detach windows from the main interface and drag to other monitors.
This is a feature of some programs, for example FL Studio, where certain windows can be detached from the main interface and dragged around to other monitors.
(see example: https://youtu.be/c9r1OqgMxhs?si=IhJwjjJXsRNZFhBK&t=16)
This could apply to all windows or even a limited selection of in-game windows such as the Map and Market.
I have no technical knowledge, so it’s possible this is outside the scope of what the engine can allow?