Is your picture of the complete, or only part of the screen?
I ask, because if I go into edit mode on the task bar, and close the “more options” part at the bottom, there is still some sort of edit panel showing at the top of the screen. And I do see a line on the task bar until I close that panel at the top.
Thank you for the reply, and sorry for my late respond.
As you can see in the snapshot (https://paste.opensuse.org/39265279), I have completed out of the edit mode, and the white line is still there.
Very strange :|…