https://gdscript.com/tutorials/classes/
Are you familiar with object orientated programming?
Basically you could create a class called Spell that acts as a blueprint. Add a variable for each property the blank spell needs to hold.
Then, in other classes, you create an “instance” of the Spell class, maybe called MyUniqueSpell and set its properties based on user input. You can have many different instances of the Spell blueprint; each with their own unique attributes.
In Godot, they say that Scenes can kinda behave as classes/blueprints too.
Of course, you can ignore OOP best practices and just use the code examples here: https://docs.godotengine.org/en/stable/tutorials/io/saving_games.html For small projects, ignoring the rules is okay.