Drupal allows to add node link into menu which is okay, if you have one menu and/or few links. When you build a site with multilingual features and create a menu per language, then your select box might grow really long. This module tries to help with this use case.
In short, this module does the following - relates the primary menu links source variable and languages, so if you edit/add a node, you get the menu dropdown which contains links in that language.
To use this module, you need to create the menus and make variable "menu_main_links_source" multilingual.