I can't add any Theater Mode skin (zip files) in the app (View > Theater Mode > Add skin), there's no error message, the skin just doesn't show up in the Theater Mode skin list
Trying the store version, it works fine
The actual folder for plugin skins:
C:\Users\Steven\AppData\Local\Packages\50072StevenMayall.MusicBee_kcr266et74avj\LocalCache\Roaming\MusicBee\Plugins\TheaterMode.List\...
However the "Add Skin" command only supports the large layout theater mode panels (eg. "Now Playing Panel"),
but not the narrow Now Playing Bar. If its the Now Playing Bar you want the skin for then try creating this folder and manually add the theater mode skin files in:
C:\Users\Steven\AppData\Local\Packages\50072StevenMayall.MusicBee_kcr266et74avj\LocalCache\Roaming\MusicBee\Plugins\TheaterMode.Embeded\...