The best replacement for footnote is endnote.

The best alternatives to footnote are rated as following:
★★★★★  endnote
★★★★  citation
★★★  bibliography
★★  reference
★  ancestry
★  in text citation
★  footnote
★  footer
★  endnote citation
★  endnotes
  endnote chicago style
  an endnote
  cite
  foot note
  asterisk
  end note

Your alternative for footnote is not listed? Suggest!
Speaking about footnote, one probably shouldn't forget about asterisk.

Other search terms related to footnote and their ratings are:
★★★★★ asterisk
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Google Trends

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footnote
endnote
citation