Hi
I am trying to add this sensor, but using the UI and not the YAML code.
But I cannot get the part right where I create the sensor
I guess this should be possible from the UI builder as well ?
This can only be added in yaml.
The “UI Builder” in your screenshot is the Automation editor… which will never create a sensor.
The closest to a sensor you could get using the Automation editor would be to create an automation that assigns the desired temperature forecast value to an Input Number Helper.
The YAML example you posted, from the documentation, is for creating a Trigger-based Template Sensor. As explained by petro, you cannot create a Trigger-based Template Sensor via the UI, only via YAML.
The screenshot you posted is an automation. As explained by Didgeridrew, you cannot create any kind of Template Sensor with the Automation Editor, only automations.
If you want to create the Trigger-based Template Sensor example from the documentation, you must create it in YAML. That means you must use a text editor to modify the configuration.yaml file and then, after saving the file, restart Home Assistant.
Are you prepared to do that?