@
jecilop - I copied '
\1 stuff' as posted by
theducks, and then replaced the '
stuff' with a bit of html for your google url.
I think the '\1' 'says' put the results of the first parenthesized search term into the destination at this place - but don't take my word for it read up on 'regular expressions' - Google for it from your jacket, I already gave you the link

(x-post with
theducks)
If you don't want it then no need for S&R, use the Comments Editor that pops when you click
Bulk Metadata Edit->Basic->Set the comments for all selected books. In Normal mode you'll see this

at the end of the second icon group, click it and you can paste a url and calibre will wrap it in gold plated HTML - easy peasy
BR