How do I delete a scrap from the curtain?
Short answer: Two-finger tap (secondary click) a tile, or use its hover trash button. Pinned scraps are protected from the two-finger tap, and deleted scraps can't be recovered.
Two-finger tap (a secondary click) on a tile to delete it, or hover the tile and click its trash button. Pinned scraps are protected — a two-finger tap never deletes them.
Deleted scraps can't be brought back. If you'd rather the gesture didn't delete anything, switch it off. See How do I turn off two-finger-tap delete?