knx virtual: D4 klix; D0 dimming actuator

I want to connect the dimming actuator D0 with the push buttons from D4 in knx virtual.

I tried the most basic setup: 

Just on/off and dimming control, with no feedback.

I linked the group adresses for ON/OFF and dimming control. But then I only get 2 buttons that only work as ON/OFF buttons.

BR_ switches the lamp OFF, BR^ switches the lamp to 100%, without dimming control.

How can I get dimming control?