For users that use only one screen to build, this is a UX nightmare. While playing the game, the mouse hovers on UEFN in the background and shows tooltip info, blocking your view. Windowed Fullscreen, Windowed and Fullscreen cause this.
Fortnite gameplay with a UEFN tooltip showing, because the mouse is hovering on it on the window behind the game.
But wait, there is more. At times the focus of the game goes away when Alt+tabbing into the game, after a few seconds, then you need to click left click to gain focus again (the mouse will hover on other screens if this happens, this didn’t happen before). This is also a problem because left click is pickaxe when inside live edit, and pickaxing things can be destructive. So we have a destructive action that is required to gain focus within live edit, every time we Alt-Tab (which happens all the time with UEFN open on live edit).
This video shows the issue at the very end. Its very fast when it happens, and its as if you clicked on another window (focus goes away from the game, then instantly comes back).
And by far the most annoying issue of all three, is when Fortnite randomly loses focus as a window, then one moment you are building in live edit, next thing your cursor is just hovering outside the window and you lose Fortnite controls. Pressing the window again re-enables them (and pickaxing), but it breaks the flow of work so much when you lose focus randomly. I couldn’t film it happening , because it has no pattern when it happens.