Today I have to ask for guidance myself in this cookbook. 
Maybe @farmio or any of you other guys has an idea how to solve my problem.
I want to use the HSL controls (Hue, Saturation, Lightness) of an MDT Glass Switch 2 (see pic below) to control non-KNX lights. So basically I have the H, S and L sliders on the KNX switch and only want to read their state into HA to use it there. (In my case I will use it in Node RED within HA, but that should not make a difference.)
I am looking for the most elegant way to do this.
I will have to receive the DPT 3.007 dimming information (4bit) from each slider, accumulate it into percentage values and send it back as DPT 5.00X status information, so the sliders on the switch move when the buttons are touched. Normally all this is done by a KNX dimming actuator, but as explained - in my case there is none.
HA’s KNX lights actually provide a HSL model. So I could create a light with hue, sat, brightness to hold the calculated status information. But unfortunately KNX lights in HA have no option to respond_to_read. So I cannot use this information to send it back to the KNX bus and update the sliders on the switch.
I know that I can solve it all with distinct event and number entities in HA for each slider. But is there a more elegant way? Maybe one that would at least hold a direct RGB or RGBW representation in HA?
Thanks for your thoughts!