How to make objects in Presenter not visible to accessibility tools

Hi, I have been tasked with making some of our courses (published in studio '13) compliant with section 508. I am quite new to this, but so far my only issue is that I cannot figure out how to hide shapes that I do not want the JAWS reader to acknowledge. These shapes do not contain pictures or text and are there for visual appeal only; I cannot remove them from the presentation because they are vital to the client's brand.

I found this link (https://community.articulate.com/series/articulate-quizmaker-13/articles/using-the-size-and-position-window-in-articulate-quizmaker), which references the "Object is visible to accessibility tools" check box in quizmaker. You simply uncheck the box to hide the object from a screen reader. I need to find this box (or some option like it) in Presenter/Powerpoint, but I can't! It seems like it should be with the Alt Text settings, but it isn't.

Also, I have read that if an image does not have alternative text, it will typically be skipped by a screen reader. Does this apply to shapes such as colored rectangles? How do you ensure the screen reader actually does skip over a shape?

Any help would be greatly appreciated. Thank you for your time!