Rightclicking on BS.Player's control panel or the video window brings up the right-click-menu on which "Playlist" is one of the options which can be selected.
The dot pl is not on playlist, but on BS.Players control panel=main window.
Rightclicking on BS.Player's playlist window (either old style or new style!) brings up a menu with several options such as adding (individual) files or (all files in) a directory=folder and it also gives you the option to "Save to file" the playlist created by you. [Use "internal format"; there seem to be some problems with text format].
Note you can also add files to the playlist by the simple drag and drop-method.
When you have created a playlist-file you can start BS.Player with the files you (pre)selected by simply clicking on the appropriate playlist file. If BS.Player is already up and running, you can load the playlist file by rightclicking on the playlist window (either old style of new style: doesn't matter) and select "Load from file".
(P.S.: Media library is empty, just like any playlist, as long as you havn't added files to it.)