When I double click on a docked panel, it collapses. I like working with the layers panel undocked so I can extend its length and be able to see more of what is in it. Ocassionaly, the layers panel is in the way and I want to collapse it. In previous versions of the beta, double clicking on the undocked layers panel would collapse it. In version 1.5.0.8, double clicking does not collapse the layers panel. I have included an image of how I position the layers panel.