You can add cross-references to footnotes via the Cross-reference dialog box in Word (References tab | Cross-reference). Note that the references update semi-automatically; to force an update you can switch to Print Preview (Ctrl+F2) and then return to your previous view (ESC).

Edit: I realize that you want to update the content of footnote 2 in your example to match part of the content in footnote 1. If you bookmark the relevant text in footnote 1 and insert a cross-reference to bookmark text in footnote 2, you can then use the keyboard shortcuts mentioned above to keep the reference updated.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional