The Catalog Tree palette shows all the schemas that are present in the Physical Schemas section of the MySQL Model page. Expand the view of the objects contained in a specific schema by clicking the > button to the left of the schema name. This displays the following folder icons:

Expand each of these in turn by clicking the > button to the left of the folder icon.

The Catalog Tree palette is primarily used to drag and drop objects onto an EER diagram canvas.

You can toggle the sidebar on and off using the Toggle Sidebar button, which is located in the top right of the application.