ThrowableProjectile

Importing the class

It might be required for you to import the package if you encounter any issues (like casting an Array), so better be safe than sorry and add the import at the very top of the file.

import crafttweaker.api.entity.type.projectile.ThrowableProjectile;

Extending Projectile

ThrowableProjectile extends Projectile. That means all methods available in Projectile are also available in ThrowableProjectile