Homematic and external Sensors

Hi all,

Posting this here since I couldn’t find any real answer on the internet. Maybe I used the wrong search idiom because I can’t imagine nobody ever wanted to feed Homematic with external sensor values.

I’m using a raspberrymatic with several thermostats one of this thermostat is directly linked to a window sensor and I can see the heating group also in openhab. This group has a channel to see the window state. So far so good.

I now would like to feed the Homematic with some external MQTT sensors so I can also decrease the temperature automatically if one of this sensors report an open window.
I remember that some time back I was able to send a command to a heating group / thermostat with openhab and it worked. Unfortunately can’t remember anymore how that worked.

Additionally I can’t find a way to create a virtual device in the CCU which I can pair to the thermostat and feed externally.

Is there really no way to feed Homematic with external sensor values and I need to implement it manually and set the temperature via openhab?