I was wondering if there is a Plugin to build more custom navigations than pages and childs … I need a few external links and links to childs from different pages…
Not sure about a navigation builder but for sure there are plenty of nice people willing to give you a hand on the forum.
No, I haven’t seen a navigation builder plugin yet. But you could build a navigation system using subpages/modules and the structure or builder field, for example. Unless you want to create a plugin yourself, of course 
To avoid a plugin in such cases I use a separate blueprint and template:
site\blueprints\link.yml:
title: Link
icon: magic
options:
template: false
pages: false
files: false
fields:
title:
label: Title
type: text
link:
label: Link to the page
type: url
site\templates\link.php:
<?php go($page->link()); ?>
If you can choose this blueprint, where you need it in the panel as a new page, and afterwards set this page visible, you can add a link to an internal or external webpage, which will be shown in the normal menu.
awesome