Final answer:
The HR Administrator can define editable HR Profile fields in ServiceNow under HR Administration > Properties.
Step-by-step explanation:
The HR Administrator in ServiceNow can define which HR Profile fields can be edited by navigating to HR Administration > Properties. This area of the ServiceNow platform is where various settings for the HR application can be adjusted, including which fields are read-only and which can be modified by users with the correct permissions. It is essential to have the appropriate administrative privileges to access and make changes to these properties.