In my version, all icons are in the vector format.
In Slate editor folder all icon files (most of them?) are raster 1x size, not 2x or more needed for the Retina support.
As you can see it’s not easy to remake this huge 4500+ (!!!) raster icons database…
Yes, I’m changing both UI and positioning, colors, UX, etc. (if it’s possible to skin myself, if not - Epic Games can consider this for future updates).