YouTube is picking up an update today to version 18.104.22.168, bringing a few different small changes to the way you interact with playlists in the app. First up is the display of playlist groupings across the app, where you now have an overflow button to save or share a list without tapping into it specifically. Each playlists now shows the number of items in the list as well.
When you're in a full playlist view, the "like" (thumb-up) button has been replaced with a plus button, which turns into a checkmark when you've added it. Playlists show up in the slide-in menu just like before, but now with a different icon and a "view all" button that takes you to your full playlist list.
It's a small set of changes, but ones that you'll like to have if you're a big playlist user on YouTube. You can grab the latest version of the app from the Play Store link at the top of this post.