Remove the single-monitor restrictions on the Scrolling layout. Each
workspace keeps a strip of its own, and a window is seen on whichever monitor
it overlaps, so placement now looks at the other monitors: a window that
scrolled out of view past an edge that another monitor is next to is hidden
instead of parked, and a partly visible one is cut down to its own work area.
A window that comes back into view is shown again first, but only the one at
the front of its container: the others are the tabs at the back of a stack,
which are hidden because they are at the back.