When you have a store with many items, the product list becomes an important database, and the ability to sort in as many ways as possible becomes really important.

However a problem arises when products are hidden in variants. If you sort by SKU, and can't see the variant SKUs when scrolling the list, you are now forced to open each product. This can be exacerbated by working in teams, where one person may use variants in a way that another might not understand.

I would envision this as an option to collapse or expand them in the list. Where sorting would order them differently than their parent, that they would be a lighter grey, and be labeled as a variant. If you open it, obviously it would open the parent. This could be animated as a way to clarify what is going on.

For example, in the site I'm currently working on, there is me, the owner and a person she hired to do all the data entry. The SKUs are all different on many of the products the data entry person chose to use as variants. Sorting by SKU when problem solving essentially shows these variants as missing products, even though they are there.

There are logical ways for us to find them, but me and the owner don't always know that something was a variant of something else.