The home/away modes on the T6 Pro cannot be triggered remotely. They’re a local feature of thermostat. To get access to the thermostats special features like enabling auto switchover, switchover threshold, humidity reporting, min/max setpoints etc you’ll need this special DTH: [RELEASE] Enhanced Z-Wave Plus Thermostat Device Handler - Honeywell, GoControl, CT, Linear, Trane, MCO
If you’re using it with SmartThings you actually should disable the setback feature on the thermostat and instead control it through SmartThings to synchronize the temperature setpoints with your hub mode using an app like this one: [RELEASE] Mode Based Thermostat - Control Multiple Thermostats Temperature / Remote Temperature Sensors when Changing Modes