Menu Level Permissions
This module restricts users from editing top-level menu items in specific menus, while still allowing them to manage items further down the menu structure. Administrators can configure which menus and how many levels to restrict, requiring an additional permission for users to edit those restricted levels.
Drupal core has an all or nothing approach to menu administration. Modules like Menu Admin per Menu provide per menu permission divisions. In really large sites though, there may be a need to restrict users from editing top level menu items but allow them to add/edit menu items lower in the structure. This module provides that ability.
Features
This module allows site administrators restrict editing a chosen number of levels of certain menus to users who have an additional permission. Folks editing any level of the menu still need to have the core administer menu permission or a menu-specific permission from Menu Admin per Menu.
Note this module is focused on menu link content permissions. Module and profile added menu links are not currently restricted in the same way. Contributions welcome!
Post-Installation
This module does not do anything unless you select one or more menus to be restricted. When configuring, the site administrator selects the menus to be restricted and how many levels of the menu are restricted. (e.g. just the first top level links, the first two levels of links, etc)
In order for users to be able to edit restricted levels of links, they need to be assigned the permission from this module.
Additional Requirements
You just need core.
Recommended modules/libraries
This pairs well with the "Menu Admin per Menu" module.