nestedpages-custom-field-filters.php

add_filter('nestedpages_quickedit_custom_fields', addCustomPageFieldsLeft, 10, 3);
function addCustomPageFieldsLeft($fields, $post_type, $column)
{
	if ( $column !== 'left' ) return $fields; // fields may be added to the left and right column
	if ( $post_type->name !== 'post-type-name' ) return $fields; // add fields based on post type
	$fields = [
		[
			'key' => 'field_name', // The meta key name
			'label' => __('Custom Field', 'wp-nested-pages'), // The label for the field
			'type' => 'date', // date|text|select
			'format_save' => 'm/d/Y', // Required for date (PHP)
			'format_datepicker' => 'mm/dd/yy', // JS Datepicker format
			'required' => false, // Validates true|false
			'validation_message' => __('A value is required.', 'wp-nested-pages'), // Displays if validation fails
			'choices' => [] // Array of choices for select fields
		]
	];
	return $fields;
}