I am using the React theme and have this issue. I have read several posts from a few years ago about this bug which was supposed to be fixed and all threads are now closed, however when I update the reordering of variants it saves and then reverts back to the original.
I have two product options (product code and length). Option "Length" has two possibilities: A and C. I am adding a new variant with Length = B. I want to reorder the list of Lengths to be A, B, C but it always reverts back to A, C, B.
Christine here from the Shopify Guru team - thanks for reaching out!
You are able to re-order the variants in the variant settings of the product:
Here is a document from our Shopify manual about how you can do that: https://help.shopify.com/manual/products/variants#changing-the-order-in-which-variants-are-shown-on-....
Hope that helps! Let us know if you need anything else. We are just a click away :)
I ended up speaking with a Shopify expert who helped me figure out what was wrong in my case so perhaps it will work for you. I have two drop down menus for my product options; first is style and second is length.
For styles A, B, C, and D I offer 2 lengths, 28" and 32". Recently I started offering length 30" in style C only and Shopify would always display as 28", 32", 30" instead of incremental order.
It turns out that I needed to have style C as the first item in the first drop down menu of styled (I.e styles C, A, B, D) in order for the reordering of lengths to work. In my case it wasn't a big deal to do this since there is no set order I need for the styles. However this may not make sense for everyone's store.