Functionality similar to Preload of Godot

So here is what am facing.
My player has an abilty. that ability spawns a projectile object.
The ability script will be added to the players arsenal as the game progress.
How can I reference the projectile object for the ability within the abilty script.
I cant fine a way to reference it manualy in the inspector since there its not on a gameobject to drag n drop it.

Scriptable object is a good way.

Addressable is also a good way depending.