The Drag a link to Tagger into the Finder toolbar screenshot was driving me nuts because it’s not that simple. I dragged, and the link just bounced back to the application. So I tried some keyboard combinations (since the screenshot indicates that it’s possible), and sure enough, COMMAND-OPTION is the magic pre-drop key combination! Of course, now I’m used to it in my Finder sidebar, so I don’t need it in my toolbar, but it’s nice to know I can do that when I want.