Well, then.
I was using the $AURA_Create() function in the ProcessSpellTargetOverride Hook before there is a $TargetContext(). I know I can add a user defined parameter, three of them according to the documentation, but how can any of them be the target? Perhaps this will make sense after some more "trial and error", becaise it is not clear to me now.
I guess I really don't understand what you are saying as to the user defined slots. The function, $AURA_Create() has 3 user defined parameters. If you mean the ARUA_Create Hook and it's parameters, I don't understand how using a parameter helps if I can't use any contexts.