For security reasons, because Zentail communicates with numerous systems based on SKU value, once a SKU value is saved in Zentail, it cannot be changed.
If you would like to change the value of a SKU, let's say from SKU-ABC to SKU-123, you can Clone the SKU you want to edit and then archive it. You will now have a new SKU with all the same information as the original.
How to Clone a SKU:
Go to the Catalog, search for the SKU you want to clone, and click on it to select it.
Click the large gear icon at the top left of the left sidebar.
Enter the new SKU value.
How to Archive a SKU:
Go to the Catalog, search for the SKU you want to archive, and click on it to select it.
Make sure the inventory in all warehouses is set to 0.
Click the large gear icon on the top of the left sidebar.
A popup will ask you to confirm that you wish to archive the SKU. Click Submit to confirm.