To rename a Sort Key or User Sort Key on a Stock Record:
In Dimensions, open the relevant Stock record.
Click the red Dimensions icon in the top left of the screen.
Click Language/Description, Load Current Window. This will open a separate Language Entry window containing all the available fields and their field lengths.
Select the required field.
In the top ribbon, click the Edit icon in the top ribbon. The field text will then be highlighted in blue at the bottom and you can rename it.
Click Save and close the window. You will then see the changes on the Stock record.