Footnote number does not support numbers above circle 1 1, which is indirectly realized. Select the footnote number in the document, set the font size to 1, and the font color is consistent with the background color of the page. Then manually enter 246a-ALT+X to get circle 1 1, set it as superscript, delete the serial number in the footnote text, and use the same method.

If you don't use automatic numbering, you can set it with custom labels-symbols, references-footnotes-footnotes and endnotes (small buttons in the lower right corner of the ribbon), but each footnote needs to be set once.