On the sidebar, click on Configuration > Functions. Then click on the Add button located on the top of the page. The Add Function dialog will be opened.
The following information can be found in the Add Function dialog:
•Name: The unique name of the function. This field is mandatory.
•Description: A description of the new function.
•Tier: The tier of the function. The tier represents how relevant the functionality is. Select the most suitable tier from the dropdown menu.
•Additional Parameters: The This is a private feature checkbox can be used to define this function as a private feature. If set to private feature, this function will not be retrieved by child instances pulling the latest definition from the instance.
After all relevant information have been added, click on the Save changes button to create the new custom attribute.