Attachment Fields to Edit Demo

attachment_fields_to_edit_demo.php

<?php

add_filter( 'attachment_fields_to_edit', 'attachment_location_field', 10, 2 );
add_filter( 'attachment_fields_to_save', 'save_location_field', null, 2 );


function attachment_location_field( $form_fields, $post ) {
	$field_value = get_post_meta( $post->ID, 'location', true );

	$form_fields['location'] = array(
		'value' => $field_value ? $field_value : '',
		'label' => __( 'Location' ),
		'helps' => __( 'Set a location for this attachment' ),
	);

	return $form_fields;
}

function save_location_field( $post, $attachment ) { 
	if ( isset( $attachment['location'] ) ) {
		update_post_meta( $post['ID'], 'location', sanitize_text_field( $attachment['location'] ) ); 
	} else {
		delete_post_meta( $post['ID'], 'location' );
	}

	return $post;
}