So…
If a scene is running (it is enabled), it must first be disabled in order for another one to start, that is, a shutdown must also be done with the scene (it can be time-dependent or even button-controlled or both)…
Two temperature ranges are specified for me (16-17 economical and 19-20 pleasant), this requires four scenes:
- turns on when the temperature is less than or equal to 16
- turns off when the temperature is higher than or equal to 17
- turns on when the temperature is less than or equal to 19
- turns off when the temperature is greater than or equal to 20.
They must be used in pairs: as lower and upper limits.
The gadget only monitors the limit values and switches on or off when they are reached.
If one of them (16-17 degree scene) is not needed, must be disabled, the other one (19-20 degree scene) must be started.
In any case, the running scene must be switched off in order to start another one or intervene manually.
Yes, if you want to switch anything manually, you also need a scene that turns off the currently running scene… 
In my case, this is even combined with a time: every 4 hours it switches back on the 16-17 degree scene so that we don’t forget the heating… and a trigger element with an RF capable switch, so that the scene change can be remotely controlled…
It works…
I recommend the web interface for editing, it is much more transparent than the app, although the scenes containing temperatures (the 4 limit values to THR316D) can only be created in the app for now.
Running 16-17…
Running 19-20…
