In the desktop client? Unlikely, Sonos has decided not to develop either the Mac or Windows clients further, in favor of mobile device clients. In fact, they removed the ability to set up new Sonos devices from the desktop clients.

Windows can do this already by right-clicking on a file and Casting it to a Sonos device.

As Bruce says, chances of any feature changes to either desktop app is slim to none.

Not continuing desktop-based clients seems like a bad idea.   Especially, where there are preferences but also people with disabilities that may not use a mobile device.   

What they should do is open-source the code and let others continue developing it -- or around it.

Not necessary, there are already many third party Sonos apps that run on the desktop, including mine.

I wasn’t aware -- can you provide names/links of these third-party applications?

Sonos is fairly sensitive about advertising in these forum, so controlav is relatively careful about exposing too much, but you could look in his profile. 

Or simply do a search on the respective “stores” pages. 

I’m on MacOS -- I didn’t see much in the respective store.  Perhaps there is something external that I’m missing.  Looks like there isn’t any private messaging here, either, which doesn’t help :) 

 There is private messaging.  Click on the person’s name, then click send message.

Totally eyeroll on myself; sorry, I did not see that :)