Intuitive ontology visualization is a key for their learning, exchange, as well as their usage in conceptual modeling and semantic database schema design. OWLGrEd is a visual tool for compact graphical UML-style rendering and editing of OWL 2.0 ontologies. We describe here the extensibility features for OWLGrEd that allow tailoring the editor for specific ontology-based modeling needs, including custom entity annotation visualizations and description of integrity constraints for semantic database schemas. We discuss the application of concrete OWLGrEd extensions in the context of ontology-centered information system engineering.