This issue has been closed as 'Won't Fix' due to an extended period of time without updates. If this issue is important to you please let us know by posting on the AnswerHub or UDN, and Epic will re-open the ticket for further review.
Opening the launcher as administrator will make it so that you cannot drag and drop fbx files into projects
Expected: The file could be dragged and dropped into the content browser
Result: When ran as admin, the file cannot be added via drag and drop
Head over to the existing Questions & Answers thread and let us know what's up.