VELBUS VMBDM in combination with slider control

I installed a VELBUS system and I have a question concerning dimming of a VELBUS dimmer with a slider. Does anyone know what kind of slider I can attach to the VELBUS, make/brand?
I noticed the option in the VELBUS link software to dim the light with sliders, so you can dim the light directly at the correct level, instead of pushing a button to change the light level, but in the manuals I can’t find any further explanation about this technique.

This is implemented in the software, for future use.
At this time, there are no sliders available.