The YouTube Music implementation in the Sonos app contains what YouTube (i.e. Google) chose to implement via the Sonos API. I don’t have YTM installed, but from reports it is one of the least complete music service implementations. It would therefore not be a surprise if this feature is not implemented. I don’t know that for sure, though.
Your other options would be to use Airplay if you have iOS devices, or Bluetooth. Bluetooth could be used via a Sonos Roam or using a Bluetooth receiver with a Sonos device with a line-in port.