The WD’s playlist capability seems to confuse a lot of people. When you get around to addressing the shortcomings they have identified, consider adding support for the following.
Imagine I have a USB drive with the a file called mit-linear-algebra.m3u with the following contents:
http://www.archive.org/download/MIT18.06S05_MP4/01.mp4
http://www.archive.org/download/MIT18.06S05_MP4/02.mp4
http://www.archive.org/download/MIT18.06S05_MP4/03.mp4
http://www.archive.org/download/MIT18.06S05_MP4/04.mp4
http://www.archive.org/download/MIT18.06S05_MP4/05.mp4
http://www.archive.org/download/MIT18.06S05_MP4/06.mp4
http://www.archive.org/download/MIT18.06S05_MP4/08.mp4
http://www.archive.org/download/MIT18.06S05_MP4/09.mp4
http://www.archive.org/download/MIT18.06S05_MP4/10.mp4
http://www.archive.org/download/MIT18.06S05_MP4/11.mp4
http://www.archive.org/download/MIT18.06S05_MP4/12.mp4
http://www.archive.org/download/MIT18.06S05_MP4/13.mp4
http://www.archive.org/download/MIT18.06S05_MP4/14.mp4
http://www.archive.org/download/MIT18.06S05_MP4/15.mp4
http://www.archive.org/download/MIT18.06S05_MP4/16.mp4
http://www.archive.org/download/MIT18.06S05_MP4/17.mp4
http://www.archive.org/download/MIT18.06S05_MP4/18.mp4
http://www.archive.org/download/MIT18.06S05_MP4/19.mp4
http://www.archive.org/download/MIT18.06S05_MP4/20.mp4
http://www.archive.org/download/MIT18.06S05_MP4/21.mp4
http://www.archive.org/download/MIT18.06S05_MP4/22.mp4
http://www.archive.org/download/MIT18.06S05_MP4/23.mp4
http://www.archive.org/download/MIT18.06S05_MP4/24.mp4
http://www.archive.org/download/MIT18.06S05_MP4/25.mp4
http://www.archive.org/download/MIT18.06S05_MP4/26.mp4
http://www.archive.org/download/MIT18.06S05_MP4/27.mp4
http://www.archive.org/download/MIT18.06S05_MP4/28.mp4
http://www.archive.org/download/MIT18.06S05_MP4/29.mp4
http://www.archive.org/download/MIT18.06S05_MP4/30.mp4
http://www.archive.org/download/MIT18.06S05_MP4/31.mp4
http://www.archive.org/download/MIT18.06S05_MP4/32.mp4
http://www.archive.org/download/MIT18.06S05_MP4/33.mp4
http://www.archive.org/download/MIT18.06S05_MP4/34.mp4
When I select that file it should play those videos in sequence.