New > Import Classonomy from File
This feature is available from the global New Button and is designed to handle large OWL ontologies that contain thousands of classes but no instances. This is a pattern that is often used in biopharmaceutical ontologies such as those from BioPortal.
TopBraid has been designed under the assumption that classes describe groups of similar instances and that there are far more instances than classes. Some key algorithms such as the GraphQL engine assume that the (class) schema is smaller than the instance graphs.
The Classonomy importer converts OWL classes into SKOS taxonomy instances, which is arguably more useful anyway. The OWL class axioms will be preserved during the conversion, in case you still want to query them.
See Also
Further Reading on New Button
Further Reading on TopBraid