Default Drupal behavior allows you to create a new link, under a menu tree item of your choice, at the time of saving a node, as below.
Have I understood right? - What you want to do is, be able to select a menu tree item, just like in the above image, but not have to enter title and description etc. You don't want new menu item created, but use the existing one, and have its path value changed from
front to the path of the new node?
^ If that is the case, you have to create a quick custom module to do so. A good idea would be to form alter (the fields, the submission behavior) the same form in the image above. That way you do not have to code the menu tree loading and selecting parts etc.
Hope this helps.