How could I make scrivener import / download a web page (when I drag the URL from the address bar of the browser to an item in the Binder)?
You are not alone. See this recent thread: Importing Web Sites. AFAIK, the simple and very disappointing answer is that the current versions of Scrivener for Windows simply do not work well for directly importing Web pages. If anyone can offer any useful suggestions on this, I also would like to hear them.
Thank you for the link.
Yes, copying the web page content to the clipboard and pasting it to the editor does not work either and I could not find another way.
I sometimes make screenshots (to the clipboard) and paste the image to the editor, that is quite convenient and fast. Or save the web page as PDF (or use an online service) or another file type and drag it / import it to Scrivener.