There is still some confusion on different appearances of Oracle SQL Developer Data Modeler. I hope this will explain a bit.

There are two different appearances of Data Modelers: the one integrated in Oracle SQL Developer and the standalone Data Modeler. And they do look different and using them is different. If you want to design the databases I would recommend the standalone version. I would use the integrated version mainly as a viewer to Data Modeler.

Integrated version:

http://www.oracle.com/technetwork/developer-tools/sql-developer/overview/index-097090.html

Standalone:

http://www.oracle.com/technetwork/developer-tools/datamodeler/overview/index.html