Nodes are linked with each other using a ID variable.

This ID can be whatever string you want.

An ID cannot reference multiple nodes of the same type in the same scene. ex :

• 2 BulletPattern cannot have the same ID
• A BulletPattern and a TriggerContainer can have the same ID.
• 2 BulletPattern can have the same ID if they are in different scenes that never interact with each others (still, not recommended)

If a node tries to get another node with its ID but this ID doesn’t reference any node, it will cause an error.

If you have a scene with some of the nodes/resources having IDs, and that scene needs to be instanced multiple times, it will cause an error because it means they will be multiple nodes of the same ID in the same scene. To avoid that, you can change the ID dynamically when the scene is instanced. But that can only be done in the _enter_tree() function.

If you don’t know how to use _enter_tree(), watch

Awesome Godot addon to make any bullethell game! (Godot 4 & 3) BulletUpHell: the basics