Show all objects - disable HideFlags

ChangeHideFlags.cs

using UnityEditor;
using UnityEngine;
using UnityEngine.SceneManagement;

public static class ChangeHideflags
{
    [MenuItem("Tools/Show All for Selection")]
    static void ShowAllChilds()
    {
        var t = Selection.activeTransform;
        ShowAllInChilds(t.gameObject);
    }
    
    [MenuItem("Tools/Show All for Loaded Scenes")]
    static void ShowAllChildsInScene()
    {
        for (int i = 0; i < SceneManager.sceneCount; i++)
        {
            var roots = SceneManager.GetSceneAt(i).GetRootGameObjects();
            foreach (var r in roots)
            {
                ShowAllInChilds(r);
            }
        }
    }

    static void ShowAllInChilds(GameObject go)
    {
        foreach (var c in go.GetComponentsInChildren<Component>())
        {
            c.gameObject.hideFlags = HideFlags.None;
            c.hideFlags = HideFlags.None;
        }
    }
}