Is it possible to add variation to existing listing that is not mine

Hello, recently was trying to add a variation to an existing clothing listing (the listing I want to add it to is not mine) . My variation is just a different size (I have XXS) and on the listing only S and L are available.

I tried to use variation wizard to add the size with the unique GTIN and it gave me the spreadsheet download which I then uploaded to the "Add Products via Upload" portion. It was successful but when I go into my seller dashboard and look at my products, it brings me to a completely new product page that is not attached to the original Parent variant that I was trying to add the "child" variant to. It appears as its own page with no product picture, or anything.

I want to have it simply as a size variation on the existing listing that is already on Amazon.