The following code was injected into GlobalManager.Update() in Assembly-CSharp.dll using dnSpy v6.1.8 (was inserted at line 17):
The keycode is hardcoded, but can be modified (reference https://docs.unity3d.com/ScriptReference/KeyCode.html for more information).

    if (Input.GetKeyDown(KeyCode.L))
    {
        Singleton<BookKeeping>.shared().clockOutPlay();
        Singleton<GlobalData>.shared().isLevelTestingMode = true;
        Application.LoadLevel("LevelTestScene");
    }