This is not really going to help you, especially if your playlists are arbitrary lists of files, but I'll tell you what I did to see if it gives you any ideas.
I had a similar problem. I am using a DLNA controller on an iPad and had set up some audio and video playlists. Unfortunately, they do not appear under the specific Audio and Video menu entries, but as a separate item called Playlists. This seems counterintuitive.
Fortunately, my Playlists were either Smartlists that selected files with certain attributes, or they were "Favourites" lists of certain categories. Therefore I turned the whole thing on its head and created these lists as separate custom views under the specific Audi and Video menu items.
To convert my Favourites lists, I used the Rating field (which I was not previously using) and set it to 5 Stars on the ones I want to appear in my list (there were about 100 items), then just created a view with a rule that only selected the ones with 5 stars.
I was probably using Smartlists in the wrong way and these lists of mine should have been set up using custom views in the first place and, like I said, if you have playlists that are lists of arbitrary items which you just like to drag and drop into, it might be more difficult to convert them into views. You would need to assign a field in the library to flag whether you want that particular file to be included in a particular list.