Good evening, @mark_schmidt ...
Could you give us some more information about your question? Is there a specific external app that you would like to add? A complete list of available LTI external apps can be found on the EduAppCenter website. Many of the apps listed here do have a cost to them (but a handful are free). Also, not every app adds a button for the app to the course navigation. It really depends on how the developer has designed the app.
If you could come back to this topic to provide a few more details for us, that would be helpful....thanks! Looking forward to hearing back from you, Mark.
