Whenever I try to import images into the editor, even the smallest images take a noticeable amount of time to import, and worse, larger images take an extremely long time. I can import these exact same images into Unity however in seconds.
I just did a test with two cubemaps that I have made for skyboxes. I dragged and dropped both images at once into Unity and Unreal:
Unity: About 10 seconds
Unreal: 20 minutes!
This isn’t an exaggeration. I wasn’t timing things with a stopwatch, just the clock, so I can’t say down to the second but I dragged and dropped them into Unity and it was pretty much instantly imported, but the Unreal import started at 9:20 and finished at 9:40.
Would you mind actually posting this in the Bug Reports section of the AnswerHub? This seems a little odd and I would like to get this assigned out to one of the support staff to take a look at when they can.