nested-inlines and django-suit
Nested inlines is something that isn't supported across the board, as it's not really part of the Django forms system (which is what the Django admin is based on). I'm sure this may change in the future, but for now the simplest thing you can do is just use multiple admins. It means saving in one form, then going into another to add data which links back to what you've just saved, but you'll probably find that more functionally reliable than, what might end up being a hacky way of getting nested inlines to work.
You could create your own workflow by overriding some of the model admins' view methods, so if the admin has just created a user, they'd be redirected to the admin for assigning books to that user, etc. You can edit the change templates for each model to add extra buttons, so you could have "Save and Manage Books" to the standard array of "Save" buttons in the user model admin, etc.
I have installed django-suit for my admin. the main reason was django suit tabs.My model contains Students, each student can have multiple Projects and multiple Books, each book or project have multiple specific deadlines ( in the future ). so I need a nested-inline, I found plenty over pypi and tested some.
I have some questions:

Why there isn't a built-in nested-inline for django? is there a reasonable explanation?
I had problems integrating nested-inline packages with django suit? anyone have experience doing that?
Is there an alternative to using nested-inline packages? (I found one, it includes creating a link to second level model, but it will mess up the process )
the admin user wants to create a student, then add for example two projects and two books, then for each book the admin would like to add 10 reports ( with a deadline ), the only way of doing that is using inlines? or I can find some other ways?