The idea is that by pressing SUPER+LEFT the current window is placed on the left of your desktop.
As mentioned, XFCE doesn't support this out-of-the-box, but it's very easy to implement:
And that's pretty much it the whole script. You'll need to install xdotool which is what does all the magic. To add your own shortcuts, got to "Settings -> Settings Manager -> Keyboard -> Application Shortcuts" and add your own.
As you can see in the screenshot, I saved this script as /usr/bin/window-placer
The options for the script are: -u (up), -d (down), -l (left), -r right & some combinations like -u -l (upper left corner) and so on. The --offset-y and --offset-x options are important if you don't want the window to hide the panels.