There is a magnetic sensor for a dock mode somewhere on the back of the phone. I know the car dock is on the side of the phone in the back directly opposite the volume buttons in a line through the Moto logo on the back. Try putting a magnet along that line and maybe you'll find the spot for the desktop dock mode.
You can also buy the desk dock uh, which should launch the Daydream mode that you want, just like the BB.
PowerDock for Motorola Droid Mini, Droid Ultra, and Droid Maxx | Griffin Technology - that has the magnet in the proper place and orientation when you place the phone.
That was designed to do precisely what you want. The wireless charging was not - it was designed to charge the phone and then stop the charge to protect the phone. If you really want daydream mode overnight while charging, then buy the device that was designed to do just that.