The code responsible for retrieving the icon for a variable in the blueprint editor palette fails if the icon is not part of FEditorStyle, meaning variables of custom types get an ugly default checkered brush.
I have a plugin and have registered icons for UMG widget types through FClassIconFinder. This works fine in the UMG designer palette, but not in the blueprint variables palette.
This line here seems to be the issue. The fix appears straightforward - the chain of calls just needs to return a brush pointer directly, rather than brush name.