Hi, that's interesting, there's no easy way to do that. What you can do is load Canvas.aspx, then (in Firefox) right click on your app's iframe --> This Frame --> Open Frame In New Tab. That should preserve all of the OAuth params we send down and you can modify the URL via the browser.
In IE I think you can right click the iframe, select Properties and get the iframe's src. Copy/paste that into a new tab/window.
Not ideal but I hope that'll work for you.
Chad