I’ve been doing some digging on what’s possible regarding masks on UMG’s Background Blur widget, and it seems that there’s really no easy solutions to it. This is especially weird because really, for a UI blur widget, one would expect the ability to make it line up with the actual UI.
The target case here would be to be able to specify an image (and potentially RGBA channel) to use as a mask (or power multiplier?) on each Background Blur instance.
I’m pretty sure this has been on Epic’s to-do list for years, and I’ve seen them talk about it in the past, not to mention the countless other community members I’ve seen bringing it up, so I really do feel this should start happening sometime.