There are quite a few posts requesting this feature for Chromecast, but as far as I can tell, not for Google Home devices, hence this post.
The spotify app on mobile and tablet devices, and apparently the web version on Chrome (although this doesn't appear to be the case for me), is capable of connecting to any Google Home devices on the same WiFi network. However, on the desktop version of Spotify, the only way to see these devices is to be playing music on them already.
This means that I have to either say, "Hey Google, play music from Spotify," each time, or use my phone to connect and switch audio over from my desktop to the Google Home device. It would be a far more seamless user experience if I could simply choose the device from the Devices button on the Spotify desktop app.
For clarity, I am using a Windows 10 PC and a Google Pixel 2 along with a Google Home and Google Home Mini. All of these devices are connected to the same WiFi network when at home.