I realize this is not something Cryptic likely foresaw happening very quickly, but some of us have reached a point where we have so many costumes that the Costume Quick Change window is now taller than our screens. This makes it difficult to select costumes at the top and bottom of the list, and it will eventually result in complete inability to select certain costumes using the Quick Change window. A scrollbar should be added to that window so that if the window's height goes above the resolution of the player's screen, people can still select from all of their costume options, not just most of them, without having to go to the tailor.
I don't know exactly the difficulty and feasibility of implementing something like this; I realize people play STO at many different resolutions. But it's something I think Cryptic should look into.