you can see the cities you are reinforcing via the Garrisons tab in your war council, the most recent hit will be at the top if you havent lost all troops there in a raid, if you did the raid will show as a total loss on your battle reports 

As Morteeee mentioned you can see them in your garrison tab in war council.

 I understand your suggestion as at times is difficult to go and check multiple pages and making sure you remember to send reinforcements back especially if you are sending over a 100 reinforcements  in your own coalition or alliance of coalitions and you wish at least in your coalition things to be easier to deal with.

This can maybe be looked into it by developers and see if they can come up with something if this feature is used by many players and not only few i guess.