A property tree user interface permits user assignment of values to metadata properties and user navigation of data, within a system that includes a data storage subsystem in which data items are organized and queried by way of properties. The property tree includes nodes that expose properties of data items. A user may interact with the property tree in order to effect an assignment of a property, in which case the value associated with the property in the data storage subsystem is modified. User input with respect to the property tree may also be indicative of a query of data storage, in which case a browsable view of data items responsive to the query is displayed. The property tree may also display nodes that represent folders within a hierarchical file system, nodes that represent properties with inherent hierarchy, and nodes that represent user-defined hierarchical properties.