As far as I know, theres nothing you can change with the spells or class description/UUID to change the animation. I believe you have to change the animation blueprint of the every body type that can use the class you are creating.
Sorcerer animation are the default for every single body to cast spells, even arcane trickster use this animations for their spell cast even tho they are an intelligence base subclass, and i believe this happen bcs in the animation blueprint of the body doesnt exit a key that say what animation to run when a rogue arcane trickster cast a spell then goes to the default which is the Sorcerer casting animation.
I know this, because monk get special animation for otherwise comon animations like unarmed strikes, the "spell" is the same any class will use, but the only ones displaying a different animation are the monks.
It is possible to overwrite, create or modify this blueprint like in this mod
https://www.nexusmods.com/baldursgate3/mods/6912?tab=files&file_id=45353 where they replaced gale human body animations for the one of the mindflayer, as of how to do it with in the manager or outside of it i have no idea
