Using keepass with mono to integration of the user's desktop is not good, so this shortcut is meant to say "when you lock the screen of kde it will closes the open databases of keepass".
You can add the ctrl + L command to it by overwriting the default system.
Using this shortcut:
$ mono /usr/lib/keepass/KeePass.exe --lock-all && loginctl lock-session
Linux Geeks doing what Linux Geeks do..