So before anyone says to just remux with MKVToolNix and change the default track, I'll explain a bit. I'm doing a lot of encoding right now, and while I wait on an encode one thing I might do is watch a movie or TV show ofc, but at that point I have limited CPU because I'm encoding and I want to use as many CPU cores as possible for the encode. I found that with the right settings a video player with a higher default priority than ffmpeg can play a lower-quality video without restricting ANY cores. So now I backup my Blurays and such twice, once for HQ and once for LQ, so I can watch while doing CPU-intensive tasks. But it would save a lot of space if I made videos with multiple video tracks, but I would have to choose a default track, and even then, potplayer will remember my last chosen video/audio track. I need to give a playlist overriding control over that if I can. It doesn't matter so much for my movies and individual videos, but I would like to make LQ/HQ playlists for my TV/Anime collection. I'm especially interested in DPL and playlists that will remember my last played file and my position in the timeline.