It looks like adding a modal UMG UserWidget to the viewport doesn’t eat input below the user widget. I’ve got a UserWidget I’m using like a modal message box (so it’s not fullscreen, it has the absolutelayout set) and it’s centered on the screen. I can click outside of the bounds of the user widget and click other interface elements while the user widget is on screen.
Which version of the editor are you currently using? Additionally, does this occur on a blank project with no additional content?
When you change the physical shape of the widget the zones where it absorbs clicks change with it. 4.5 clears this up by removing the modal option. The way around this, and the way you’d also do it in 4.5 is to make a widget that uses the center anchor point and an alignment of 0.5,0.5 to always appear centered inside a canvas who’s visibility is set to be visible (as opposed to self hit test invisible) so that it absorbs the clicks.