This was going to start out as a post telling you how to change the LG G3 button shortcuts to work with other apps and features when the phone's sleeping. Only you can't actually do that. The phone is locked to launching the camera by holding volume-down button, or Quick Memo if you hold volume-up.
Thing is, that's all you can do. There are no other options. And that's disappointing.
There is, however, the option to shut all that off — just go to Settings>System>Shortcut key and hit the on/off toggle. But that's it.
So, LG, consider this a plea for the ability to add other shortcuts. Because, really, you can't open the Android Central App fast enough.