Insert new header/footer in multiple files w Pinegrow?

I am trying to modernize an older html/css website. I bought an html/css theme, with multiple pages that I intend to adapt with my own text and images. I have successfully created my own header/footer for the index.html page. I’d like to copy this header/footer to all the other pages in the theme (i.e. do a global replacement). I’m looking for an easy way to do this. The only thing I can think of is to do some sort of simple global search and replace using Notepad++ with all my files open, but I’m wondering if there is an easy way to do this in Pinegrow? Any advice appreciated for a newbie.