Perhaps cheating here a bit, but you can get a Google play music control visible on your full screen actiontile.
1. Use chrome browser and go to your extensions. Search for the official google play music player extension. After installing, open the extension.
2. use casting extension to cast music on tab to your chromecast (audio) device. The music you are casting should now run via your chromecast (check this)
3. Open the actiontiles via a new tab, login and run full screen
You will notice the google music player overlaps the full screen and holds full functionality. Just design you tiles around it and it feels like an integrated player. A bit of a cheat, but works well and is really easy to setup.
Obviously you cannot integrate this with any triggers or automation, but I have a permanent screen that remains connected to audio and ST via action tiles. Once you want to switch off music it a simple pause and move on with your life. Back home, simple tab on play and your music takes off where you left it.
If you have the task bar pop up, you can also use windows settings to unlin taskbar as I did.
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