I have been trying to apply my own style when hovering or keyboard/gamepad focus of buttons. Everything is nearly done with the exception of the border that shows up when the keyboard has the button focus (seen in the attached image).
Thanks ZenithSal,
I’m posting a copy of the details so this can be marked as answered.
To disable the dashed border or modify its behavior you can go to Edit → Project Settings → User Interface and then look for Focus → “Render Focus Rule” (as of UE 4.8).