Hi AnandaT,
The Windows versions never had this Media Browser. It was based on third-party code and was created specifically to access media libraries of Apple/Mac programs (Apple iPhoto, Aperture and Photos etc) although it allowed the user to add custom folders to be listed there. It's functionality was rather limited and as i said, end up being removed altogether from the Affinity Mac apps in v1.7. There's plans to develop a DAM (digital assets manager) but it's something that's not coming anytime soon/there aren't much details yet.