Alternatively and a tad roundabout, save the web page as an HTML document (Web Page, complete) via ⌘S. It's really fast (in most cases), and then you can diddle with it offline to your heart's content. Nice idea, but it doesn't work.
Jon
macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365
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