In my original search for "desktop icon in Opera" I found many solutions that didn't work, so I assumed it was a difficult problem.
Now I've found that you need only shrink the web page size, grab the little icon (called a "favicon") at the left end of the address bar and drag it to your desktop.
I hope I've got this right finally. I'm trying to "pay back" to Poasters for all the great help I've previously received here.