Does anyone know how to give those skills to other classes? Like, giving Eirika’s Lord Class Slayer?
You’d need to know ASM. As far as giving Slayer to other classes go, I believe the vanilla implementation checks to see if a class falls in a specific range of the class array.
Can you tell me where to find that class array?
It’s the regular class array. If you look up the ASM code for Slayer in either JJ or Hextator’s documentation, two of the bytes used are the two bishop classes. If you change those bytes, I believe any classes that fall between those two will gain the slayer skill.
If you want to do more with skills than that, you’ll need to learn ASM.