I've managed to set up all necessary controls on steam controller. But, one issue remains.

The triggers on controller send to game throttle settings on 0, 1/3 for left trigger and 2/3 and full for right trigger.
In steam you can remap trigger and it works, but it still send throttle commands together with new mapped actions.
It looks like that steam controller triggers are recognized as one of joystick axis.

does any one knows how to disable axis for throttle in gog edition?

thanx in advance.