Waiting means that the item has yet to be matched or uploaded to the cloud. You can try right-clicking and see if Add to Library is available from the context menu. If so click it to see if that helps move things along. Try also File > Library > Update Cloud Library which should update all waiting tracks.
Duplicate indicates there is another track in your library with the same properties, normally title, track #, artist, album and album artist. You should be able to locate the other version of the track and add that to the playlist instead. See also Duplicate songs in iTunes - Apple Community. My script cannot access this cloud status property, but if you eliminate all same album duplicates from your library then you should be able to select any remaining tracks that are marked as duplicate, right-click, and add to library, to get them to be reevaluated.
A removed track is one that was in your cloud library, but has been removed from using the library on another computer or device. When such tracks are stored locally on your computer they are not deleted immediately but instead marked as removed in case you change your mind. You can right-click, and add to library, to add them back to the cloud. Once they are marked as matched, uploaded, or purchased, you should be able to add them to your cloud playlists.
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