Having a similar problem on OSX and 11.3.1. Started a post the other day about it and got no answers, and then saw this thread so it's good to know I'm not completely alone. It's definitely driving me bonkers trying to edit with any flow. Any pop up/dialogue window/audiosuite render takes the focus off my edit window and I have to select somewhere on it to get focus back and move on with editing.
Really hating that nothing can sit on top of the video window too.
Maybe 11.3.2 would fix this...too bad I have to buy PT12 to get it.