Hidden Products
If you check off "hidden product" when editing your digital product, the product will not be visible on the sidebar when a student is signed into your program unless the product was purchased or granted to the student.
If you enable the product landing page, the product can be purchased by those who know the landing page URL. Alternatively, if the product is part of a bundle, it can be purchased through the bundle as well.
As seen below, the Product List tab on your "Products" page will help you see at a glance which of your courses or digital products are currently set to hidden: