Plex doesn’t manage playlists well, when the playlist or video entry names include cross (×).
Playlists end up created, but hidden from many views in the Plex (Web) app.
Playlists appear in the list of existing playlists in the create new playlist UI, but nowhere else.
This happens even after the directories and video filenames are renamed to replace Unicode characterts with ASCII. Restarting the Plex service helps somewhat, once all of the file paths are limited to ASCII characters.