The music room tool is largely intended as an out-of-game gallery of sorts for players to listen to music. I have experimented with a playlist/queue feature myself, but I don't have anything working to the point where I would include it in this tool. You're welcome to modify it to suit your needs, but I don't have a timeline at this moment or advice on how to get a queuing system working with the tool. I also have not tested this tool in 7.4.11, and I would not be surprised if there are problems running it there as such an old version is not currently supported. I recommend you update to a more modern engine version if you can.