If your organization is not integrated with Zoho People, You can create custom user fields and also edit,disable or delete them whenever required.
Edit custom user field
To edit a custom user field, do the following:
Hover over the custom user field you want to edit and select the edit icon.
Edit custom user field form will appear. You can edit the name of the custom field and check box if you want to allow users to edit. Make the changes and select Save.

Note:
Marking field as mandatory can be done only while creating a custom user field.
Once you have checked a user field as PII or ePHI, it cannot be reversed.
Disable custom field
To enable/disable a custom user field, do the following:
Hover over the custom user field you want to disable and select the eye icon.
A banner message "Custom field is disabled" will appear. To enable the custom user field you can select the eye icon again.
Delete custom field
To delete a custom user field, do the following:
Hover over the custom user field you want to delete and select the delete icon.
A confirmation pop-up will appear. Select Delete to delete the user field.