Get all currently open editor windows in Unity.

OpenEditorWindowsTracker.cs

using UnityEngine;
using UnityEditor;

public class InternalEditorWindowsTracker : MonoBehaviour
{
    /// <summary>
    /// Get all currently open editor windows including default Unity windows, custom editors and windows that are tabbed.
    /// Found here: https://answers.unity.com/questions/1237463/how-do-i-get-a-reference-to-the-default-editor-win.html?_ga=2.133529742.1822843399.1574452927-44739247.1572947128
    /// </summary>
    public static EditorWindow[] GetAllOpenEditorWindows()
    {
        return Resources.FindObjectsOfTypeAll<EditorWindow>();
    }
}