We have released the 18.0.3 patch which addresses a performance problem with the newer version of the Java JREs running on macOS Sierra. The bundled OS X Java is now updated to 1.8.0_40-b27. We have also included several fixes in the Editor and in the Schema Synchronization tool.
Stackoverflow post explaining the macOS Sierra performance issue using Java:
For the complete list of changes, view the changelog.