Lets say u want to find "Andariel's Visage" helm with 120 dex on it
Instead of typing in the "Legendary or Set item" box and then searching thru all helms there, just set the item level (5, item type (helm), rare/legendary/magic and stats(120 dex):
I know this is common sense but it might help someone :P i used to search legendaries by their name for some time until i figured i can do it like this