GA4 connector: Is it possible to filter by pagePath without importing this dimension?

Hello dannyfig - yes, you can do this using the Power Query connector.  You will need to include the path path (so you can filter on it) but you Google's recommendation for getting the unique sessions is to also include the event name so that you can filter records where the event name = session_start. I tested this and got the same results in Power Query as I did using a Google Analytics exploration.