Google Nest thermostat HVAC modes

I currently have a google nest thermostat which works pretty well with its integration. However my mom has an iphone and im trying to connect homeassistant to homekit for her. The only thing ive run into is that she can only select heat and off on the nest (and obviously she can set the temperature). The problem then is that she cannot put it into eco mode. Considering we never turn it off by hand, is it possible to switch between eco and heat instead of heat and off?(or just add the eco mode) (I thought it might be possible to add eco to the HVAC modes in homeassistant, but I dont know how and/or if that would work). Does somebody know if this is possible? Many thanks!!

So basically I wish to add the

preset_modes: 
    -eco

to the hvac_modes

Yes, home assistant nest integration already supports eco mode – assuming the API says it supports it. You can look at the integration diagnostics and it will give some details about the traits supported by the device to get a lower level detail.

Sorry to necro this but did you ever get this figured out? I’ve just set up the nest api and I can’t work out how to expose eco mode to HomeKit either.