How to Add missing `using` using hotkeys?

[it19862]

I'm trying to add the missing using with: Ctrl + . , Alt + U. Nothing is happening. I have a code

using System;
using System.Diagnostics;

namespace Folder_NS_02
{
    public class Test
    {  
  void Main(string[] args)
  {
   List<string> ItemsLst = new List<string>(); 
  }  
 }
}

If I understand correctly, then after pressing Ctrl + . , Alt + U CS-script.npp will add to the code the line using System.Collections.Generic;. I have nothing going on.

Questions.

1. Am I doing everything right?
2. How do I do this correctly?

[oleg-shilo]

The UX is very similar to the one that you have in VS:

Ctrl+.

Alt+U