KDE's window manager, Kwin, supports this functionality built it. Just right click on any title bar on a window, go to "Special Application Settings" -> "Arran

KDE's window manager, Kwin, supports this functionality built it. Just right click on any title bar on a window, go to "Special Application Settings" -> "Arrangement and access" -> "Shortcut". You can manually type "F8" in the shortcut and it'll work just fine. You can also go to "System Settings" -> "Window Rules" to manage all rules you've defined.