Not sure if you are using my Google SDM API integration, but it supports a custom command setEcoMode. Calling this with arg 'MANUAL_ECO' enables eco mode on the thermostat. Calling the same command with arg 'OFF' reverts back to the previous mode.
Interestingly it seems the API does not support changing the eco setpoints, just uses what is already configured. Logically, the "normal" setpoints cannot be changed while in eco mode.
Looking at this part of the code now, I can see some enhancements and streamlining that I can make 
