Click the Add Delete button-Format-Superscript in the small triangle at the far right of the toolbar. Do it. That is, first type the serial numbers of 1 and 2, and then black out the serial numbers and click Format → Font → Superscript.

You can also use

Insert-quote-footnotes and endnotes. However, it is suggested that the references of the paper should not be inserted in the form of endnotes. Once the paper needs to be revised, especially when the content needs to be deleted, this insertion form is very troublesome, and editors hate to insert endnotes when changing references.