After adding the Page Tree widget, it only showed as empty. I set the parameter to my front/home page, but no pages (not even that one) showed up in the widget, nor did the buttons to "expand," "collapse," et al.
Looks like it needs updated. Doesn't work with 3.2.1, hasn't been updated in quite some time, so. I just wanted to vote it "broken," and don't expect to see a resolution posted here.