I accidentally requested the same feature! When I check a set for completeness, I sort my bricks on a table. I then take the inventory at Rebrickable and go down the list, throwing the parts in a container. If I could sort the list by quantity, I could speed this up by first removing the largest quantities of bricks from my workspace. They are often easiest to find (except for the last ones ? ). If I then, for some reason, have to clear my workspace, I don't lose much work by throwing all the unique or low-quantity parts back in a bin to continue sorting them later. I can easily record that I have gone through the list up until parts with quantity X and continue from there later.