This is a duplicate of https://issues.unrealengine.com/issue/UE-40352
After expanding all of the import settings for skeletal mesh import window it will always appear with part of the window off screen as long as the settings stay expanded.
RESULT
The fully expanded window will appear and be partially off screen
EXPECTED
The fully expanded window appears and is positioned such that the entire window is visible.
Head over to the existing Questions & Answers thread and let us know what's up.