I believe by default AwareIM will automatically add a close button even when you delete it from the Panel Operations for a form. Most likely to prevent not being able to close a form once opened.
My solution for you would be to add a close button in the panel operations but give it a very specific class and the use the following in the Render Script for that form to hide it. Please note that this will hide every single HTML element that has the same class anywhere in your app.
$(".close-BO").hide();
