I just discovered the "fill window" xfwm functionality. Wow, that is so cool. But only works if windows do no overlap ...
What would be very cool, is a "move window so now overlap occures anymore" option.
Can something like that be done in xfwm?
I'm not sure I understand you well. What you're proposing is that different windows be maximized but still not overlap/cover each others?
Xfwm is a stacking windows manager. Stacking WMs (the default in X Window System) work as if you were putting papers on your desk. Some papers are stacked, with some in front of others. Other papers are side by side.
You're looking for tiling WMs, or dynamic WMs such as dwm. In this screenshot you have 3 tiled windows in the background and 1 floating window in the foreground.
I think it's a major design change for Xfwm. You can propose the feature on Bugzilla but I doubt they'd do much with it.
You are not that wrong with me, being after tiling wms. But I tried tiling wms, they are just to limiting.
What I would love to see, is a stacking wm which has some extra functions so that I can manually place my windows like I think would be optimal.
Filling is one thing. If I place a window into a free space, I often want the window to grow into that free space, cool!
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 cool, if there would be some function that prevents this (i.E. move one window a little so that the overlap is removed).
Am I clearer now?
Check out an application called wmctrl. It's a command-line utility, that can be used to manipulate the size, shape and placement of windows. I access it by creating shell scripts that invoke it with certain arguments and binding those shell scripts to shortcut keys in Xfce's keyboard settings.