Custom Post Status Generator

<?php
/**
 * Registers the "archived" post status.
 */
function my_plugin_register_archived_status() {
	register_post_status(
		'archived',
		array(
			'label'                     => _x( 'Archived', 'post status', 'my-plugin' ),
			'public'                    => false,
			'internal'                  => false,
			'protected'                 => true,
			'private'                   => false,
			'exclude_from_search'       => true,
			'show_in_admin_all_list'    => true,
			'show_in_admin_status_list' => true,
			/* translators: %s: number of posts. */
			'label_count'               => _n_noop(
				'Archived <span class="count">(%s)</span>',
				'Archived <span class="count">(%s)</span>',
				'my-plugin'
			),
		)
	);
}
add_action( 'init', 'my_plugin_register_archived_status' );

/**
 * Adds "Archived" to the classic editor's status menu.
 *
 * WordPress registers the status but never adds it to that dropdown, so the
 * option is appended in the browser and the current value re-selected.
 */
function my_plugin_register_archived_status_editor_option() {
	$screen = get_current_screen();
	$types  = array_map( 'trim', explode( ',', 'post' ) );

	if ( ! $screen || ! in_array( $screen->post_type, $types, true ) ) {
		return;
	}

	$post     = get_post();
	$selected = ( $post && 'archived' === $post->post_status ) ? 'selected' : '';
	?>
	<script>
	jQuery( function( $ ) {
		// JSON_HEX_TAG keeps a label containing </script> from ending this block.
		var label = <?php echo wp_json_encode( 'Archived', JSON_HEX_TAG | JSON_HEX_AMP | JSON_HEX_APOS | JSON_HEX_QUOT ); ?>;
		var value = <?php echo wp_json_encode( 'archived', JSON_HEX_TAG | JSON_HEX_AMP | JSON_HEX_APOS | JSON_HEX_QUOT ); ?>;

		$( 'select#post_status' ).append(
			$( '<option>', { value: value, text: label, selected: <?php echo $selected ? 'true' : 'false'; ?> } )
		);

		<?php if ( $selected ) : ?>
		$( '#post-status-display' ).text( label );
		<?php endif; ?>
	} );
	</script>
	<?php
}
add_action( 'admin_footer-post.php', 'my_plugin_register_archived_status_editor_option' );
add_action( 'admin_footer-post-new.php', 'my_plugin_register_archived_status_editor_option' );