> You'd just have these ghost windows that can't be directly interacted with as first-class windows. But that is what the GP asked for, not full duplication.

> You'd just have these ghost windows that can't be directly interacted with as first-class windows. But that is what the GP asked for, not full duplication. Though if you want duplication it might be possible by creating a window over the duplicated area that the compositor does not render but still grabs all input events that are then forwarded to the original windows via XSendEvent.