I was struggling with the same thing, wondering why the "Remove from list" button was no longer in the app. I personally think it is annoying to have the uninstalled stuff in the lists, and would always remove them so I only had the once I had installed.
I found a solution to this though; You have to install Garmin Express on your computer. Then connect your watch to the computer, and go to the apps section. From there you can right-click on the not installed ones and remove them from the list.
