Applying Geometry Nodes to all objects in the collection

Typically, the Geometry Nodes tree in Blender is built differently for each mesh. This makes it possible to apply different effects to different objects. However, when we need to apply one effect to many objects in the scene, assigning a separate Geometry Nodes modifier to each of them and duplicating the nodes may be counterproductive. It is much easier to create a collection in which, when an object is placed in it, the desired effect will be applied to it.

Read more: https://b3d.interplanety.org/en/applying-geometry-nodes-to-all-objects-in-the-collection/