After trying to remove the menu bar from the main window using win.setMenu(null)
in the main.js file, I encountered a new issue. When opening a new window (referred to as the "add items window"), I struggled to find a way to hide the menu bar in it as well.
onclick="window.open('addNew.html' ,'Add New Item', 'width=900 , height=400 , toolbar=no ,resizable=no')