After you have acknowledged your original taxi instructions, TGS becomes active, so you will need to deactivate it (hotkey 1) before requesting the runway change (ctrl/shft/w).
I´ve deactivated TGS anyway, would that mean it will not becomes active then?
A neat trick (thanks for the suggestion Ralf) is to use CP Mode 1 at the start of the flight, so your copilot will not automatically acknowledge the first taxi instruction. You can then request a runway change without the need to deactivate TGS first. As you are taxiing to the runway you can change to CP Mode 2 for the rest of the flight.
Well you know I always use PF3 with MCE. Therefore I wouldn´t set any CP Modes. But anyway, what you say, and I really appreciate your help, is what I already knew. To restrict the runway usage on one side or request another departure RW on the other, is just some kind of workaround and usually don´t happen in real world, because the Pilots are being told by the controllers which runway is in use for take-off usually before gate departure. If not, the Pilots can ask Ground or delivery at any time, if they don´t know this already by heard the instructions given to their colleagues who departed before.
And this is something weird, because in my case at EDDH, ground give the AI-traffic departing before myself the instructions for RW 23 for take-off, but when I came to taxi-clearance I was instructed to use the 33.
Maybe it´s something for further development to build in something like this I suggested. Of course I´am already very happy with this great ATC of PF3. I even remember those days when ProFlight 2000 came along, what a great milestone in getting more immersion. The option to use MCE with PF3 is the cream hood and have the FO handling the ATC. But as always in life, what you have you don´t miss and you want even more