Enable Constraints Network on the object.

Points to a LOP node whose stage will be rendered into the Scene Viewer along with the SOP geometry when diving inside this SOP Network. Any USD cameras and lights will also become available to look through in the viewport’s camera menu. Specifying a LOP Network instead of a LOP Node path will fetch the stage of the LOP Node with the display flag set within the target LOP Network.

This SOP Network and the LOP node can be anywhere in the hip file and this feature will still work, but most commonly it comes from the LOP Network in which this SOP Network is embedded. It is also possible to create this same parameter as a spare parameter on any other node that contains SOP nodes (such as a Geometry Object) to cause a USD stage to be rendered in the Scene Viewer when inside the SOP Network.