Unable to insert footnotes in a Pages document

I cannot insert footnotes in a book I am drafting in Pages.app with a view to producing an epub. I have tried selecting a word, clicking in front of it, clicking after it, but Insert/Footnote is always greyed out

OK, I have searched similar questions, and last year another user got the following answer:

"If you are in a Page Layout document, and entering text in a Text box, then there is no footnote insertion capability. It will remain gray on the Insert menu. Footnotes are for regular Pages word processing documents."

Is this serious? I am using the "Textbook" module, and somebody thinks textbooks do not need footnotes? Could somebody please give a proper answer? And if for whatever bizarre reason footnotes cannot be inserted in a text box, exactly how else can they be added? And if I am trying to make a book copy-pasting text from a Word file, how do I enter it if not in text boxes?

Any clarification very gratefully received.