If you have come across this error “You are attempting to edit a variant with a 'Unique Id' that doesn't exist on Wish yet”, it is because you have not yet added this SKU on Wish. In order to edit an existing SKU, it needs to exist on the Wish platform.
Troubleshoot this issue: To edit a SKU, ensure it exists on Wish. To verify, please navigate to Products > View all products and search for the SKU. If it does not exist, you can add a new variation, either manually or through a CSV Upload. To learn more on how to add/edit a variant, click here.