Earlier quoted context omitted.
I can't put a playlist into YouTube kids. I tried.
Here's a video on how to do it: https://www.youtube.com/watch?v=AjKmQwhSk1s It's not exactly a playlist, but you can hand select content.
Edit: I watched the video. I’ll have another look on the app tomorrow but I’m pretty sure that video does what I’m complaining about. The catalogue is pitiful. I just want access to all of YouTube. It’s not a big ask but they won’t make $$ off of Showing adult videos to kids so they won’t offer that.