By left clicking a node in the main content pane the context sensitive pane (on the right) will change to show the options available for that node.
Right clicking a node brings up context sensitive menus for the item.
If you select an index in the main pane you will see the index options on the right side of the dialog.
Right clicking on the index folder will allow you to create a new index. But you must right click on an index if you wish to alter it. See Tables Pane for more information.
The tree view is broken up into folders and subfolders. The following are the top level folders.
Query - Execute dynamic queries.
Tables - Table related functions, including indexes
Views - View related functions.
Relationships - Display a list of the Foreign Keys.
Programmability - CLR and TSQL Procs, and CLR Assemblies loaded into the database.