Daniel Martínez Lara and José Molina are working on a Blender add-on for extending Blender’s Grease Pencil functionality. The layer manager stores the values and options from each Grease Pencil layer, and is also useful to set each layer’s visibility when you are working with lots of layers, backgrounds, different characters, etc. The add-on is expected to be made available soon for download. More on Vimeo.