Is there anyway to batch renaming via Editor [not on Runtime] multiple game objects in the hierarchy ?

Yes, it’s possible using a custom editor window. Like this:

 using UnityEngine;
 using UnityEditor;
 
 public class RenameChildren : EditorWindow {
     private static readonly Vector2Int size = new Vector2Int(250, 100);
     private string childrenPrefix;
     private int startIndex;
     [MenuItem("GameObject/Rename children")] public static void ShowWindow() {
         EditorWindow window = GetWindow<RenameChildren>();
         window.minSize = size;
         window.maxSize = size;
     }
     private void OnGUI() {
         childrenPrefix = EditorGUILayout.TextField("Children prefix", childrenPrefix);
         startIndex = EditorGUILayout.IntField("Start index", startIndex);
         if (GUILayout.Button("Rename children")) {
             GameObject[] selectedObjects = Selection.gameObjects;
             for (int objectI = 0; objectI < selectedObjects.Length; objectI++) {
                 Transform selectedObjectT = selectedObjects[objectI].transform;
                 for (int childI = 0, i = startIndex; childI < selectedObjectT.childCount; childI++) selectedObjectT.GetChild(childI).name = $"{childrenPrefix}{i++}";
             }
         }
     }
 }

To use it:

1. Save the script in your project.

2. Go to GameObject/Rename children.

3. Select the parent of the objects to rename.

4. Fill the fields and press the button.

Thanks @RaptorRush this works perfectly and exactly what i was looking for :)

I couldn't do it can you help me it gives an error