The object will not appear in the hierarchy.
using UnityEngine;
public class Example : MonoBehaviour { // Creates 5 planes and hides them from the Hierarchy in the Editor.
void Start() { for (int i = 0; i < 5; i++) { GameObject createdGO = GameObject.CreatePrimitive(PrimitiveType.Plane); createdGO.hideFlags = HideFlags.HideInHierarchy; } } }