I downloaded the 4.3 preview release from git a couple of days ago just to play around with this. Is there something like a z-index to help with layer order when items overlap?
I like where it’s heading though. Good job! Despite the lack of any real info, I took a basic 3rd person BP template and managed to throw together a pseudo menu of sorts with sliders to change bloom and contrast… that post-process node… wow, that’s a lot of connectors on a single node, but irrelevant to this topic. 
For anyone interested in trying it out, it looks like 4.3 will no longer be using the widget blueprint as an actor that you drag out into the level. To get access to it, after making your widget BP, either in the level BP or PlayerController BP (I used PlayerController EventBeginPlay), create a widget, cast to your widget BP, then call show on it to see it, and hide on it to… well, hide it.
PlayerController:
Level:
Widget:
Edited for slight clarification and to add last paragraph/photos