I think the title says it all. Whether creating a new leveledcharacter list or adding things to an existing one, I can't add in any of the custom NPCs I built. Any other actor I can add.
My actors are a custom race, if that makes any difference.

It may be the race thing? I can add actors to levelled lists no problem.

Try making a custom character that's not a custom race and see if you can add him. If you can, then you know it's something with the race.

Did it, and I could add it to the list. So if that means it's the race, what in the race would make it unable to be used in the lists? It is a copied version of another race for reference.

Solved it. Apparently creatures with scripts attached cannot be put into leveled character lists.