Do Gridmaps/MeshLibrary only contain the meshes and their associated physic bodies/ colliders? Is there no way of attaching a script to a geometry and using that in the GridMap? Is the only way of detecting where a mouse is clicking via raycast when it comes to GridMaps?

Context:
I've been working on an "isometric" game (but 3D with a rigid orthogonal camera at certain rotations) and I'm trying to determine what/where the user's mouse is clicking. The last couple days I have been playing around with raycast-ing from the camera (which is not very accurate at all) and then I learned that CollisionObject3D's have "an 'input_event' signal that will let you know when it was clicked"!!!? This is wayyy more accurate but I can't seem to access/attach this function to my Gridmap/MeshLibrary. I've tried attaching a script to the root node of the particular scene that contains one of my "tiles" and to the PhysicsBody in my scene (AnimatableBody3D) to emit this info.

https://preview.redd.it/oe6515o2rowc1.png?width=532&format=png&auto=webp&s=1e182a8546454bda7a0069e0603817c6b9b252ab