I'd like to create my playlists offline, on my home PC and transfer these to my Car PC. This mostly works; I create playlists in .wpl format, leaving out the "tid" tags, because I don't know how to create them outside of WMP.

These playlists play fine in WMP, and allow me to circumvent a SD limitation: I can now play tunes with Unicode filenames (as long as they don't contain Unicode tags).

BUT, these playlists will not show up in SD until opening and saving them in WMP. What's the magic here? Is it the tid tags that appear after saving the .wpl file? Or is it the WMP library? Is there any way to automate this?