There may be a way to play a favorite via a simple POST command to the SmartThings REST API, but that’s one command I haven’t exposed yet. I got several commands working in the limited time I’ve spent tinkering with it, but not that one … yet.
Some years ago, I started running node.js on Raspberry Pi and installed jishi’s code to control my household Sonos system. It’s still running today and remains my go-to as it has all the advanced capabilities (and more) that I could want for controlling my system. Plus, the Pi being a always-on local device, a playlist can be invoked via a group preset or to a single device by making a simple one-line request like this:
http://localhost:5005/living room/favorite/myplaylist
These and other requests can easily be included in Routines and Scenes in SmartThings (but not SharpTools, which does not have local access) using a Edge Driver like this one.