There is any app to download YouTube videos placed on a playlist?

I'm way too distracted when I'm on YouTube but there is a ton of amazing content there. I'm looking for something that could download/sync the videos that I place on a playlist like a private one or even the watch later and then be able to see those videos on something like Plex. There is anything like that available?
Just to be clear, I don't want to download the whole channel, just selective videos that I may find interesting.