You can attach more than one script to a character/object though. Maybe the slots you're talking about are something different.
For things like onDeath, you don't necessarily need to use scripts attached to characters at all. The story scripts grab most of that if you setup an event for it. They do it all the time for the basic systems included in the SHARED scripts.
I'll also add the same advice I tell everyone about using the D:OS editor. The D:OS editor is really made to make Divinity games. Within that context, it does a pretty good (and fast) job once you get to know it.
