Yes it's working fine. But I wonder why this extension doesn't allow saving the same item to more than one group. Any reason for this? Is it the same in the Firefox version?

Done!

I think that's what you get on Google Chrome with the Diigolet. Or you can just use the "Save Bookmarks to Diigo" button. Diigolet is collapsible, and the save button fits on the same line as the address bar.