This article explains why you shouldn't change the SKU value for listings in your Etsy shop that is connected to Gelato.

When you add a new listing from Gelato or connect an existing listing to Gelato, a connection is established between your Etsy listing and Gelato's platform using the SKU value. This connection is essential for order fulfillment and inventory management.

Changing the SKU in your Etsy Shop Manager will break this connection, and Gelato will no longer be able to process orders for that listing.