Unity : How can i run a script in in edit mode (Not Runtime) when i select some object, and i wish to receive user input (Edit update loop) and Instantiate and object on key-press ?

RunScriptInEditModeAndReciveInput.cs

using UnityEditor;
using UnityEngine;

//How can i run a script in at at edit time (Not Runtime) when object is selected, and recive user input (Edit update loop) ?
//Editor scripts have to be in folder named Editor
//[CustomEditor(typeof(GameObject))] ensures that this peace of code will run only when we have GameObject selected so we are save to cast object to GameObject [selectedTarget = (GameObject)target;]

[CustomEditor(typeof(GameObject))] //This is custom editor for the type GameObject ( This script will kick in when we have game object selected )
public class CubeEditor : Editor
{
    private GameObject selectedTarget;
    const float radius = 4f;

    //This functions runs only one when we click the object.
    private void OnEnable() //Similar to start in MonoBehavior
    {
        //this will be always be true ( we are safe of doing this cast )
        //The target is the keyword suplied by the Editor class and it means the selection 
        selectedTarget = (GameObject)target;
        
        SceneView.duringSceneGui += CustomUpdate;
    }

    private void OnDisable()
    {
        SceneView.duringSceneGui -= CustomUpdate;
    }

    public override void OnInspectorGUI() //this method is run several times a frame as soon there is a change in the scene
    {
        base.OnInspectorGUI();
        Debug.Log(selectedTarget.name);
    }

    void CustomUpdate(SceneView cv) //out custom function, ran every frame frame during Unity's editor (to achive this we add it to delegate) 
    {
        //Debug.Log("CustomUpdate has been tied to the SceneView.duringSceneGui  delegate!");
        Event e = Event.current; //It'can be anything

        if(e.isKey && e.character == 'g')
        {
            GameObject instanciatedCube = (GameObject)PrefabUtility.InstantiatePrefab(Resources.Load("Cube"));
            //instanciatedCube.transform.position = selectedTarget.transform.position + Random.insideUnitSphere; 
            instanciatedCube.transform.position = selectedTarget.transform.position + (Quaternion.Euler(Random.Range(-180.0f, 180.0f), Random.Range(-180.0f, 180.0f), Random.Range(-180.0f, 180.0f))) * Vector3.forward * Random.Range(0.1f, radius);
            //When dealing with quaternions the order of operation is important in multiplication
        }
    }
}