Greetings @FlemmingVesterg ,

Thank you for posting on the Instructure Community!

Navigation links are usually added either by external apps that are configured that way, or by using the redirect tool, which is an app that allows you to add a custom navigation link to your course navigation (you get to choose the link, the name, etc).

If you are looking to add an app that is not on Canvas as an external tool / app that appears on the course navigation, I recommend using the redirect tool!

Hope this helps,
Noah