How to add more dropdown items or top level menu item in the default navbar?

I'm playing around with the software and I was trying to modify the "Navigation Clean" default block. I did manage to modify the menu entries but I can't figure out how can I add more top level items or more dropdown items. I'm stuck the default 4 top level ones and the 3 nested in the dropdown.

The Overview menu has (as I'm expecting) the entries locked so I can't duplicate them to add one or two entries. Should I create from scratch my own navbar to have more menu entries?

Solved as I kept looking the right hand pane menus for an option, there was a plain add item button in the top bar of the interface.