Hello! I am overstocked in certain sizes, and I want to run a flash sale. I am trying to create a collection where you can see only certain product variants (e.g., all T-shirts size 3x+). However, it appears that I can only add products, not variants, to a collection. Is that correct? I know I can split my products up in regular and large sizes, then add the large sizes product to a collection, but that's messy for a lot of reasons :(. Any help or troubleshooting ideas are appreciated.