To change the orientation of your Smart Radiator Thermostat's display, please do the following in the tado° app:
Go to Settings > Rooms & Devices, and
select the respective Smart Radiator Thermostat.
Then select the desired display Orientation: Vertical / Horizontal.
Please note: If your tado° app is not showing the Orientation option, you won’t be able to select / change the display orientation of your Smart Radiator Thermostat. This means that your hardware version doesn’t support this option.