A Unity Editor Window that does some simple asset renaming

Renamer.cs

using UnityEngine;
using UnityEditor;

public class Renamer : EditorWindow {

    #region Variables

    private GameObject[] targets = new GameObject[0];

    private bool debugThis = false;
    
    private string prependValue = "";
    
    private string appendValue = "";
    
    private string replaceTarget = "";
    private string replaceValue = "";

    #endregion

    #region Starts

    [MenuItem("Window/Renamer")]
    private static void Init () {
        Renamer window = (Renamer)GetWindow(typeof(Renamer));
        window.titleContent = new GUIContent("Renamer");
        window.Show();
    }

    #endregion

    #region Interaction

    private void Rename () {

        for (int a = 0; a < Selection.objects.Length; a++) {

            string assetPath = AssetDatabase.GetAssetPath(Selection.objects[a]);

            if (!string.IsNullOrEmpty(assetPath)) {

                string assetName = Selection.objects[a].name;

                if (debugThis) {
                    Debug.Log("assetPath: " + assetPath);
                    Debug.Log("assetName: " + assetName);
                }

                if (!string.IsNullOrEmpty(prependValue)) assetName = prependValue + assetName;
                if (!string.IsNullOrEmpty(appendValue)) assetName = assetName + appendValue;
                if (!string.IsNullOrEmpty(replaceTarget)) assetName = assetName.Replace(replaceTarget, replaceValue);

                if (debugThis) Debug.Log("new assetName: " + assetName);

                string error = AssetDatabase.RenameAsset(assetPath, assetName);

                if (!string.IsNullOrEmpty(error)) Debug.LogError(error);

            }

        }

    }

    #endregion

    #region Process

    private void OnGUI () {

        this.Repaint();

        GUILayout.Label("Select your target assets in the Project window");

        GUILayout.Space(10);

        EditorGUILayout.BeginHorizontal();
        prependValue = EditorGUILayout.TextField("Prepend With:", prependValue);
        EditorGUILayout.EndHorizontal();

        GUILayout.Space(10);

        EditorGUILayout.BeginHorizontal();
        appendValue = EditorGUILayout.TextField("Append With:", appendValue);
        EditorGUILayout.EndHorizontal();

        GUILayout.Space(10);

        replaceTarget = EditorGUILayout.TextField("Replace:", replaceTarget);
        replaceValue = EditorGUILayout.TextField("With:", replaceValue);

        GUILayout.Space(10);

        debugThis = EditorGUILayout.ToggleLeft("Debug Changes", debugThis);

        if (GUILayout.Button("Rename")) Rename();

    }

    #endregion

}