Thank you very much gentlemen for all your suggestions and Art-J is correct: it WORKS...
BUT:
it needed some experimenting to find out the correct keys to use and what I did for that was to reprogram the command with another button on my keyboard if which I thought it would not be used for anything else..
But what happened was a bit strange. I use a QWERTZ German layout and replaced the \ shown in the list of commands by ´ (accute accent) onyl to be surprised by what that produced! It showed = as a result, but that is actually above the 0 (zero) on my keyboard.
OK, I thought, let´s find out what they use to produce the \ and oh miracle: I found the # is used for that .... !!
So, now that I know that, I have reset the command to the original backslash and use the number sign # on my keyboard to produce that - and it actually works!
It is pretty obvious after this experiment that the command table refers to the the U.S. layout, because there the \ is on the button above the right shift (where the German layout has the #) and the = is just left of the backspace button, where the German has the ´
So, PROBLEM SOLVED!
For others with similar problems: check the key assigments in the general settings and also for the individual airplane you want to fly, because they MIGHT differ.
Thank you all, I can now call the ground crew and get my chocks set ;-)