Hi @StephenBryant01 ...
You're not alone in wondering why some apps don't appear in the "Installed" tab. I've often wondered that myself. It seems to me like if a specific app doesn't require a Consumer Key and a Shared Secret (I compare this to a Username and Password), then if you install the app to your course, it will show up under the "Installed" tab. Take, for instance, the "Redirect Tool". That LTI does not require a Consumer Key and Shared Secret. So, once you click on that app to install it into your course and configure the options you want, then it should show up in your "Installed" tab. But, other apps that do require the Consumer Key and Shared Secret may have slightly different ways to install the app...and so because of that, my educated guess is that those are not showing up under "Installed" for one reason or another. For the most part, I always go to my "View App Configurations" button...because I know for certain that's where I can find the true source of what is installed either at the account level or at the course level...depending on where I'm currently looking as a Canvas administrator.
Hope this helps in some way.