Tab based multi-level Menus in J2

I am working on J1 based application that has tabs/panes bases multi-level
menus on page as.

Dashboard | Finance| HR | Admin

As user clicks say Finacne there is another row of sub-menus of Finance as:

Statments | Claims | New Queries | Graphs

and then clicking Claims will show another row of sub-menus for Claims.

I need to implement same navigation in J2. What i learned so far is J2
navigation is based on actual Portal Resouces (Pages, Links, Folder).
Folders are listed in Left navigation pane by default while all PSML pages
goes as menus on top of page. These can be customized however what to
display in left nav pane or menus.

How can i created sub-menu when clicked on a menu? Is there any example for
this?

Thanks