Certain default (or "core") checkout fields have aspects that cannot be edited by the Checkout Field Editor plugin. These fields are essential to WooCommerce's checkout functionality and help preserve compatibility with other plugins as well. This article will help you identify core fields and understand what you can and cannot modify from these default settings.
Core WooCommerce checkout fields are highlighted in purple in the Checkout Field Editor settings:

Aspects of these fields that cannot be modified will show dashes instead of customizable fields in the table on the settings page (e.g. billing_postcode shown above). You're unable to edit:
With these concerns in mind, some core fields can be edited in the following ways:
Article ID: 1623
Created On: Wed, May 12, 2021 at 1:35 PM
Last Updated On: Wed, May 12, 2021 at 1:35 PM
Online URL: https://www.heartinternet.uk/support/article/can-i-edit-core-woocommerce-fields-with-the-checkout-field-editor-plugin.html