

What you did was to suppress endnotes in sections 1, 2, and 3.

Not so, you can specify that you want the endnotes to appear at the end of the fourth section, just before the index section.

You may think that you are limited to placing your endnotes at the end of each chapter or after the index. The first four are "chapters," and the last one is an index. What does this mean for you? Let's say that you have five sections in your document. What you may not know is that you can choose to suppress endnotes for specific sections of your document. Long-time users of Word know that you can place endnotes in a document, and you can specify for them to appear either at the end of a section or at the end of the document as a whole.
