Point the "edit" links in Nested Pages to the Gutenberg editor if installed.

nested-pages-gutenberg-edit-link.php

<?php
add_filter('nestedpages_edit_link', 'gutenbergEditLink', 10, 2);
function gutenbergEditLink($link, $post)
{
	if ( !is_plugin_active('gutenberg/gutenberg.php') ) return $link;
	$link = admin_url('admin.php?page=gutenberg&post_id=' . $post->id);
	return $link;
}