The comfort/sport knob adjusts the dampening of the shocks on the GX. Sport is a bit firmer. This is not related to KDSS. KDSS is a system that connects to the anti-sway bars to either lock in and reduce body roll, or allow the wheels to move more independently (although not entirely disconnected) from the sway bars. KDSS is a nice option for those that don't want to do big lifts from what I understand.
It is likely that KDSS is still installed with the coil spring setup, and it is also likely that OEM shock were not used so the ride comfort switch will do nothing. Many report that the ride with coils and aftermarket shocks is just as good as the air bag system. but you do lose the height control and the auto leveling during towing/heavy loads. Some install aftermarket airbags inside the coils (airlift or firestone) and attach it to the original system to gain some of this functionality back.
120-Series Toyotas | IH8MUD Forum is a good resource for the GX470 as well.