Yes, I always fold my sheets and the fitted ones are no problem. I pin them to the line by the 2 short ends. Fold and bring up the bottom and pin that by the same cothspin. then take off 1 clothpin and fold in half and keep folding that way and they are perfectly folded and go on the shelf. My daughter -in-law was dumbfounded when she saw me fold a fitted sheet. She said she didn't think you could fold a fitted sheet.
And she said she never knew anybody who did fold a fitted sheet. So she learned something from me.