I don't really write skins so please pardon my termonology. This involves an old issue I found but it's the same in the latest MM beta (old issue was detailed here: http://www.mediamonkey.com/forum/viewtopic.php?f=9&t=42104
If you create a button to utilize the PlaylistButton call in the micro player the playlist that pops up is empty, but only if you go straight from the Player to the MicroPlayer. If you go from the Player to the MiniPlayer and then to the MicroPlayer, it functions as expected (minus the fact that the window is slightly transparent half of the time). From what I can tell in MicroPlayer mode the BtnPlayList call in the popup always works but the PlaylistButton call only works if you go to the mini player prior to the MicroPlayer.
The link to the old version shows how to mimic this easily, but please let me know if any more information is needed. This issue prevents someone from quickly navigating the entire playlist in the MicroPlayer. Waiting for and navigating the popup is very time consuming, sometimes it doesn't show, and the playlist when you finally get there isn't resizeable, so the work arounds are pretty painful.