Hello junghoonshin,
I face the same problem and an internet search brought me here. In the meantime, I may have found a small solution to your issue if you have not already resolved it:
(in Markdown, use Latex to superscript the footnote number)
First part$^1$
(and the next one)
Second part$^2$
(at the end of your text add *** to create a line across the document)
(under the line, add the text below:)
1, 2: Text for your footnote
It works to a degree, but will not hyperlink the footnote numbers to the footnote text (like it would normally) - but if you have only a few footnote numbers for the same text, does it really matter.
Hope that helps - and if you found a better way, let us know.