I have a very large number of products and many of my products have many  color and size variants.

I can import the product and all the attributes but is there a way to import the product attribute combinations, because it is almost impossible to edit them manually?  
As the SKU, gtin and the inventory quantity are stored under the product attribute combination how is inventory managed?
How do other websites manage very large catalogues with variants?
Is there anything you can recommend?
Does the Premium support services (3 months support period)  include this feature?

Waiting for your response