How to add new spellbook tab ?

[Khira]

Hi everybody,
I try to add some spells and I need to add new tabs in the spell book. I know where are take informations about the name of the tab (SkillLine.dbc) but if I try to add a line, i have any new tab in game.
I think i need ti edit another file or something else but i don't know where is it.

So, if you have any idea, thanks.