Hmm..
Tested it several times, let the game run ten days first, then killed him through console and the title remains inside your realm and gets inherited
by Gerhard Chatenois, the duke of Upper Lorraine, just as it says in the tooltip before death.
PS: Still i recognised , that before letting the game run a few days , that initially it is indeed mentioning the king of Jeruasalem as heir
and that he also indeed inherits, AS LONG as i don't let the game run a bit before killing the king of Lotharingia.
Probably that old bug/issue where the game doesn't recalculate inheirtance in time or correctly and where reloading often helps.
Might be a memory issue, might be a scheduling inheritance check issue, i don't know..
You could still report it.
Can't hurt. Who knows, maybe we still get a patch some day and maybe they'll do find a way to address the issue.
Dreams can't hurt, even the cruel ones.
Ach, I done messed up. I forgot the HRE comes with princely elective. I'll craft a new one.