AsdfEditor.cs

using UnityEngine;
using UnityEditor;
using UnityEditor.SceneManagement;

[CustomEditor(typeof(asdf))]
public class AsdfEditor : Editor {
    asdf Target { get => (asdf) target; }

    // https://docs.unity3d.com/ScriptReference/EditorGUILayout.html
    // https://docs.unity3d.com/ScriptReference/GUILayout.html
    public override void OnInspectorGUI () {
        DrawDefaultInspector();

        if (GUI.changed && !Application.isPlaying) {
            EditorUtility.SetDirty(Target);
            EditorSceneManager.MarkSceneDirty(Target.gameObject.scene);
        }
    }

    // https://docs.unity3d.com/ScriptReference/Gizmos.html
    // https://docs.unity3d.com/ScriptReference/Handles.html
    // https://docs.unity3d.com/ScriptReference/IMGUI.Controls.BoxBoundsHandle.html
    public static void DrawGizmos (asdf customTarget) {
        Handles.matrix = customTarget.transform.localToWorldMatrix;
    }

    void OnSceneGUI () {
        DrawGizmos(Target);

        if (GUI.changed && !Application.isPlaying) {
            EditorUtility.SetDirty(Target);
            EditorSceneManager.MarkSceneDirty(Target.gameObject.scene);
        }
    }
}