I have about hundred entities/tables and I would like to navigate right to a particular entity/table in the diagram. Is there a way to do it?

Yes. In Browser right-click on the entity/table name you want to navigate to and select Go To Diagram.

 

If your entity/table is in several diagrams they all are shown to you. Select the diagram you want to see. Now you will have that diagram opened and the entity/table selected.