i dont know, if i understand your question right,
do you mean levels = Subfolder?
Then there is no limit in levels.
The *.npl file looks like this:
So, there is no problem with different sub-folder in a playlist.FILE D:\Musik\Nightwish\Tales from the Elvenpath (2004)\04-nightwish- bless the child.mp3
FILE D:\Musik\Synasthasia\Synasthasia - Scotias Death.mp3
FILE D:\Musik\Nightwish\Tales from the Elvenpath (2004)\08-nightwish- stargazers.mp3
It works perfect for me in NMC 07 ALPHA2a