AkelPad 4.9.8 x64 won't go away when it loses focus, either by clicking in another window or by using Alt+Tab, on Windows 10. It will lose focus (title bar will be gray) but it will remain on top of the newly focused window. If AkelPad is maximized, you can't see anything else other than AkelPad, even if you use Alt+Tab, and you need to minimize it or move the window elsewhere.
Please let me know if there's any other info I might provide to help.