You're trying to restrict the field Region inside Accounts using Code List Restrictions, but the field is not available on the option Code to Restrict.
SAP Hybris Cloud For Customer
The field Region is not supported to be restricted using Code List Restrictions functionality.
This is an expected system behaviour.
If you need this functionality urgently you may contact your implementation manager to help with such request or approach directly the SAP Cloud Service Center (firstname.lastname@example.org).
Note: The services of the SAP Cloud Service Center will be charged as packaged services based on fixed prices.
An alternative option may be to check the SAP Customer Influence Site to submit an idea: https://influence.sap.com/SAPCloudforCustomer
Code List Restrictions, Code to Restrict, Region, Accounts , KBA , LOD-LE-BP-BP , Business Partner , Problem