SftTree/OCX supports "flat" lists only in virtual mode.  Hierarchies cannot be represented in virtual mode.

The tree control can be used to display flat lists (without hierarchy) with up to 2,000,000,000 items.  Graphics, colors and all tree control data and attributes are provided by the VirtualItem event, which the application must implement to use a virtual data source.  This eliminates lengthy initialization when many items are to be displayed.  Virtual mode is enabled using the VirtualMode property.