It would be nice in a stacking WM like xfwm4 to have extra functions so that one can manually place all windows optimally, similar to a tiling wm.
The "fill window" keyboard shortcut is very helpful in that sense. I often want a window to "grow" into the given free space.
But it fails as soon as two windows overlap only a little bit. That, if I "fill" one of the windows, it "overtakes" the other window. So it would be nice, if there would be some function that prevents this by moving and resizing the windows such they do not overlap anymore.