How to search for positions?

When I am reviewing a game, how do I search for the current position in the lichess database? (I see imrosen do this in his streams, but maybe he uses a tool outside lichess?). I see the search page (advanced search), and it does have a 'position' in one of the pull-down menus, but I haven't figured out how to specify the position I'm searching for.

If you're in a game, under the moves list there's a little book. If you click on the book, it'll show you whether games with that same position were found, and stats along with it.

Is this what you were looking for?