I implemented the idea from
to use Keyboard Maestro to peek behind my active Window.
The only problem with that is that the minimizing takes ages.
But konfluenzpunkt from AptGetUpdate came up with another idea based on the original.
He moves the Window to the buttom of the screen and moves it back afterwards.
The only problem I had in the beginning was that my masks did only display numbers for moving or resizing the window.
Till I figured out that you can just click in the mask and enter the text manually.
After that editing the macro was easy.