How to </body> or </head> to find and replace code?

Auto replace code in Webflow using or custom code.

Must swap <div {attributes-A}> with <div {attributes-B}
and ref: background video link to my own ftp background video link.

How do I accomplish this with webflow custom or




The above are some basic examples for illustration, as not all things can be patched with a custom-html element. I currently do this by exporting webflow as zip file and find folder containing html file and edit and re-up it, but there;s got to be a much simpler way by simply doing a swap replace rule within or .