Caius' Blog What is it, 2003?
Posts with the tag unreal:

Workarounds for darkening effect on disabled UMG widgets

Three Weird Tricks To Get Around That Gray Disabled Effect In Slate/UMG (Tim Sweeney Hates Him!)

Global shaders in Unreal without engine modification

Leveraging scene view extensions and modules to add custom global shader passes the “right” way.