here is an explanation of what we have:
multiple simple products for each t-shirt, we use an attribute set with color, size and sex.
The end product is a designed t-shirt, it has a pattern image and must take the t-shirts from the inventory (that's why we use a configurable product)
So, we have around 100 different simple products - but even more configurable products (each pattern gets it's own so the number is huge).
But what when we create a new simple product - let's say a blue t-shirt L sized which we didn't have prior to creating the configurable products. Is there a way to add the associated product to multiple configurable products at once - and not have to go into all products to add it?