Is it possible to inspect the Firefox browser GUI using the new built-in Developer Tools? I used to be able to do this with the old DOM Inspector by selecting File > Select Chrome Document. I could then click through the list of DOM nodes and the corresponding part of the Firefox browser interface would light up (e.g. toolbar buttons etc.). I cannot seem to find a way to do this with the new built-in Firefox Developer Tools. The inspector only seems to inspect web site page content, and not the Firefox browser itself.