Ubuntu Mate on new 7" touchscreen

I use the latest version together with the new 7" touchscreen. I had the problem with this screen, that for a normal screen view I must add a new line in the config.txt.
The problem is here, that I miss the possibility of the function “raspi-config” to configure some special functions on the raspi.

This might help?:

The problem on raspi display is that we don’t know exactly if we have one GPU with a screen 1 on HDMI and a LCD as screen 2 or if LCD as an other GPU.

If we have just ONE GPU, so having two screen to work together is not very hard, we just have to define them in xorg.conf with 7" touchscreen as a 800x600 display part of virtual 1920x1080 display.

In fact, for me, 7" touchscreen and hdmi on my TV are both active (my TV sea a input) but i only see my desktop on my 7" touchscreen because of lack of configuration in xorg.conf.
Y will try to test some config to see if something happen.