Rasagar/Library/PackageCache/com.unity.terrain-tools/Editor/TerrainToolbox/TerrainGroupInspector.cs

using UnityEditor;
using UnityEngine;

[CustomEditor(typeof(TerrainGroup))]
internal class TerrainGroupInspector : Editor
{
    Terrain[] childTerrains;

    public override void OnInspectorGUI()
    {
        TerrainGroup groupTarget = (TerrainGroup)target;

        EditorGUILayout.Separator();
        groupTarget.GroupID = EditorGUILayout.IntField("Group ID", groupTarget.GroupID);
        EditorGUILayout.Separator();
        if (GUILayout.Button("Update Child Terrains"))
        {
            groupTarget.UpdateChildTerrains();
        }
    }
}