Hi,
There's a behaviour in this plugin I noticed that is different to how Joomla behaves and therefore is more restrictive. In the Joomla menus, it is possible to have 2 or more menu items on the same level with the same alias as long as they're in different languages. However, the Add to Menu plugin won't allow those menu items to be created (complaining that the alias is already in use) so one can only create the item with a different alias, go back to the menus and correct it, which defeats the purpose a bit.
Cheers,
Agata