The Editor on Mac will display progress bars on top of other application windows when the Editor is in the background and does not currently have focus. This can interfere when attempting to do other work while waiting for the Editor to complete a task.
During the move process, the Editor will display progress bars on top of the application window that currently has focus.
The progress bars will be displayed on top of the Editor window, but behind any other application window that currently has focus.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-72207 in the post.