A sort key is used to list the actual database value associated with a particular option in a drop-down. For example, when you are trying to create a customer of type sold-to 0001, if the sort key is not enabled, you would face a screen like this.
This results in confusion and makes the whole process error-prone for the end-users.
Solution : The key used to internally identify the actual field needs to be enabled. Goto ‘Customize Local Layout’ in the SAP GUI and select ‘Options’ from the drop-down.
In the pop-up that opens-up go to the far right top corner and select ‘Expert’ from the drop-down. Make sure the two check-boxes ( Show Keys in All Dropdown Lists” and “Sort Items by Key” are checked on. 
Apply and click OK. You can see the result in the drop-downs immediately – The Keys are enabled and sorted in alphabetic order.
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