So what you do is setup your smart search index to get everything by default so you can perform dynamic filtering on it as you navigate into the pages.
For instance, say you have a URL like so:
/Partners
/Partners/USA
/Partners/Europe
/Partners/Australia
You sent your base smart search index to look at /Partners
. In the webpart you configure your Path property to be a macro by clicking the black arrow and entering {CurrentDocument.NodeAliaspath%}/%
What this will do is get all the pages below the current selected page. So if you're on the /Partners
page, it will get all the partners below. If you're on the /Partners/USA
page, it will get all the partners in USA. The key is to have your smart search set at a high level so it indexes them all so you can filter later on.