The window drawing feature works similar to plan9's rio window manager. To use it, press Super+Shift+D or click on the far right of the blue window title indicator. Your cursor will change to a cross-hair. You can now drag out a rectangle and letting go of the left mouse button makes the current window take that size. You can also draw on different monitors. Clicking on a different window while in drawing mode will move the current window on top of it and copy its dimensions.