Youtube Music does not provide a function to go back within their website. This functionality is provided by the "Back" function of the browser. So it would be nice to also have a "Back"-Button (and may be a "Forward"-Button) within the sidebar player. I think such a feature fits easily into the title bar of the player (right next to the refresh button).

I also tried keyboard shortcuts, but ALT-Arrow-Left seems also not working within the sidebar player.