An other possible solution is to add a filter that only shows scrolls in excess of a given number.
It would be more flexible than a tab showing scrolls in excess of 3 only.
(For instance players that want to keep 3 copies for decks and 3 for trading, thus only selling scrolls in excess of 6. To the contrary, new players may not have/want 3 copies of each scroll and would prefer to get gold by selling scrolls in excess of 2...)
BTW, 4Robato's suggestion is even better IMO since it's more flexible and would make trading much easier (not having to remember what scrolls we wanted to keep or trade).
(Anyway, these 2 suggestions aren't incompatible with each other... :P )