Add hero ability to Spell Book

I've been fiddling around with spell books, trying to use one to trigger-activate a hidden evasion. The problem is, I can't figure out how to add Hero abilities to the spell book. When I open up "Data - Spell List" in the Object Editor it only brings up the categorical options "Unit" and "Item". I currently don't know of any other method to add spells to a spell book. Is there something else I need to do before Hero abilities become available? Perhaps a Stat I need checked True? I tried different combinations of "Stats - Hero Ability" and "Stats - Item Ability" to no avail.

Thanks for your help.

Seriously if checking Stats - Hero Ability to false didn't work you would have to use Shift to introduce the rawcode directly.

If you mean changing the ability I'm trying to add to the spell book to a plain unit ability, I was trying to add a hero ability while keeping it a hero ability. Anyways, it's more or less resolved (your answer was helpful, too, thanks.) Apparently it can be added by tricking it - either through rawcode like you said, or by pretending the ability (you're trying to add to the spell book) is a unit ability and then switching it back to a hero ability once it's added.