Make a new folder called 1x1 and put them in there. They appear on the 1x1, 1x4x4, and 1x1 plate.
The aspect ratios on 1x1s and 1x1 plates are different, if you print a properly scaled 1x1 print on a 1x1 plate, it will appear stretched on the 1x1.
There isn't any way to have it appear only on the 1x1 and 1x4x4 lists, you'll just have to deal with people being able to make them appear on 1x1 plates.