I've found that it's possible to ask GH is a device is on or off:

"Hey Google, is the master bedroom light on?"

(google will answer yes/no. For dimmers, it answers "yes" if the device value is > 0)

I can also tell GH to set a dimmer to a particular level:

"Hey Google, set the master bedroom light to 10%"

My question is, is it possible to ask GH what level a dimmer is set to?