For those in need:

using UnityEngine;
using UnityEditor;
using UnityEditor.EditorTools;
using System;

namespace Kamgam
{
/// <summary>
/// Thanks to https://forum.unity.com/threads/4-6-editorapplication-modifierkeyschanged-how-to-find-out-which-key-was-pressed.357367/#post-2705846
/// 7+ years later and we still need this.
/// </summary>
[InitializeOnLoad]
public static class GlobalKeyEventHandler
{
public static event Action<Event> OnKeyEvent;
public static bool RegistrationSucceeded = false;

static GlobalKeyEventHandler()
{
RegistrationSucceeded = false;
string msg = "";
try
{
System.Reflection.FieldInfo info = typeof(EditorApplication).GetField(
"globalEventHandler",
System.Reflection.BindingFlags.Static | System.Reflection.BindingFlags.NonPublic
);
if (info != null)
{
EditorApplication.CallbackFunction value = (EditorApplication.CallbackFunction)info.GetValue(null);

value -= onKeyPressed;
value += onKeyPressed;

info.SetValue(null, value);

RegistrationSucceeded = true;
}
else
{
msg = "globalEventHandler not found";
}
}
catch (Exception e)
{
msg = e.Message;
}
finally
{
if (!RegistrationSucceeded)
{
Debug.LogWarning("GlobalKeyEventHandler: error while registering for globalEventHandler: " + msg);
}
}
}

private static void onKeyPressed()
{
OnKeyEvent?.Invoke(Event.current);
}
}
}

This design decision is bonkers.

Example: if you want to make an editor window that uses shortcuts you have to artificially focus and element just to get key events which a very brittle way of doing this due to inputs also requiring (and sometimes stealing) the focus. You should provide and easy way of getting global key events while the user focus is INSIDE the editor window. Not matter what specific element is currently focused.

This makes it really hard to create custom editors using UI Toolkit when I can't rely on key events to fire.