@pclaudel1: Yes I can replicate this, sort off anyway. When I open Opera Developer it does not open full screen and the Opera icon and menu is missing from the top left hand corner as you say. To get it to appear I either have to resize the window by either maximising the window fully or by resizing the window from the borders. Once I do that resizing by whatever means it appears.
Opera is up to date
System:Manjaro Linux (x86_64; XFCE)