The Alexa.ThermostatController Interface supports a
schedule object with an 'until' or 'for' appended to the command. See
https://developer.amazon.com/en-US/d...ontroller.html. I don't use the Resideo skill for TCC as I have my own Alexa skill that controls Evohome via a HGI-80 and I support this possibility because it's trivial to do so. I can also cancel this timed override with 'Alexa, resume thermostat schedule' which is also supported by the Interface.
Are you sure Resideo don't support this? Their docs are (of course) lacking, but maybe the command is there nevertheless. Try "Set livingroom to 20 deg for an hour" and see if it tells you it's supported.