Multiple MENUITEMs Multiple Editor windows

I’m trying to set up multiple menuitems and multiple editor windows. I’ve been able to display one window, but when I add any more it spits out an error.

public class ToolMenu : EditorWindow
{
    [MenuItem("Cool Tools/Item Database")]
    	static void ItemEditor() 
    	{
    		EditorWindow.GetWindow(false, "ItemEditor");
    
    	}
    [MenuItem("Cool Tools/MOBDatabase")]  //This was the old way..
    	static void MOBEditor () 
    	{
    		MOBEditor mobwindow = (MOBEditor) EditorWindow.CreateInstance(typeof(MOBEditor));
    		mobwindow.Show();
    	}
    
}

In general avoid using methods that take class names as strings.

The GetWindow method can only open one instance of a Window as it will open and return the existing instance it there is one.

So for EditorWindows where you only want / need one instance you should use GetWindow:

[MenuItem("Cool Tools/Item Database")]
static void OpenItemEditor() 
{
    GetWindow<ItemEditor>();
}

For windows where you want to be able to open multiple instances you should use CreateInstance:

[MenuItem("Cool Tools/MOBDatabase")]
static void OpenMOBEditor () 
{
    MOBEditor mobwindow = CreateInstance<MOBEditor>();
    mobwindow.Show();
}