Aaaaaand the soltution is:
Instread of
- homematic:HmIP-BDT:a8faecaa:0008DA498E78FB:3#LEVEL
i should have used
- homematic:HmIP-BDT:a8faecaa:0008DA498E78FB:4#LEVEL
Or in readable words, i had used the Dimmer Transmitter; I should have used the Dimmer Virtual Receiver Channel.
So, the problem was sitting in front of the Keyboard.
No i have to find and fix a different issue: if i set the light to 100% is OH, it is still rather dim :-/. Probably i have to touch the channel logic…