A manual for writers of research papers, theses, and dissertations, Ninth edition - Kate L. Turabian 2018

Use footnotes and endnotes judiciously
Drafting your paper
Research and writing

If you are using notes-style citations (see 3.5.1), you will have to decide as you draft how to use footnotes and endnotes (for their formal requirements, see chapter 16). You must cite every source in a note, of course, but you may also decide to use footnotes and endnotes for substantive material that you don’t want to include in the body of your text but also don’t want to omit. (You might also use such substantive notes in combination with parenthetical citations in author-date style; see 18.3.3.)

✵ ▪ If you cite sources in endnotes, put substantive material in footnotes. Otherwise you force readers to keep flipping to the back of your paper to check every endnote to see whether it is substantive or bibliographical.

✵ ▪ Use substantive footnotes sparingly. If you create too many, you risk damaging the flow of your writing with asides and digressions.

In any event, keep in mind that many readers ignore substantive footnotes on the principle that information not important enough for you to include in the main text is not important enough for them to read in a footnote.