The tabs are found on both the Profile and Messages pages.
The feedback reminder is programmed to notify you once a trade is completed, thus if you provide feedback to your trade partner before then you'll still get the reminder. It's happened to me every time since I give feedback once I receive cards - though I do not close out the deal until both of us have marked it as received.
Follow my blog - I Identify as a Card Collector.
“Aslan didn't tell Pole what would happen. He only told her what to do. That fellow will be the death of us once he's up, I shouldn't wonder. But that doesn't let us off following the signs.” - Puddleglum in The Silver Chair by C. S. Lewis