Currently, to see the values of variables stored on a page, you have to actually add printouts somewhere, either on the page or in whatever template(s) set the variables you're interested in. This is annoying and (in the case of templates) can result in unwanted printouts accidentally being saved. A better method would be some one-click method to see all variables stored on the current page with their (final only?) values. Semantic MediaWiki has a similar feature for semantic annotations, Special:Browse (example), and this has been invaluable for helping to debug SMW stuff.