Let's assume that your salesman wants quick access to the Quotation menu from the Sales menu. You can organize a menu hierarchy using Odoo Studio. Click on the Sales application, enter studio mode, and you will have an Edit Menu button on the top, besides the configuration menu.
Click on the Edit Menu button and a popup will appear that has the menu structure of the Sales application:
You can drag and drop the menus to organize the order. You can see in the preceding image, I have dragged Quotation from its position, and I'm about to drop it just below Sales. The indentation of the menu is important to define the parent-child relation of the menus.
