This is perfect, will absolutely achieve the needful. I will definitely use this going forward in my future documents.

Just one follow-up question on this: Not knowing the way to do it with find and replace, in the current document I've already added the () manually, to 150 of 340 footnotes in this document. If I now do the find and replace command you've given, it will add the () to all, including adding an extra set to the ones I've already done. Won't it?