Thinking about it, setting a label should work:
Number:Temperature Heizung_Buero_Solltemperatur "Solltemperatur [%.1f %unit%]" <temperature> (Heizung_Buero_Group) { channel="zwave:device:cef8b92dc5:node16:thermostat_setpoint_heating" }
I’m not sure where that default comes from, though … I checked the zwace binding code and it doesn’t seem to be defined there.