Variant order in the Customer Portal follows the variant position you've set in Shopify. To update it:
In your Shopify admin, go to Products and open the product.
In the Variants section, drag and drop variants into the order you want (e.g. Small > Medium > Large).
Save the product.
The updated order will sync to Skio and reflect in the Customer Portal the next time the product is loaded—no changes needed in your Skio dashboard.
This applies everywhere variants appear in the portal: the swap dropdown, product picker, product detail view, and upsell carousels.
If a variant doesn't have a synced position, it will fall back to alphabetical order.