How do I scroll through scraps in the curtain?
Short answer: Move your pointer toward either end of the strip to scroll that way (faster near the edge), or use two-finger trackpad or mouse-wheel scrolling. A chevron shows when more tiles are hidden.
Just glide your pointer toward either end of the strip — it scrolls that way, faster the closer you get to the edge. Two-finger scrolling on a trackpad and a mouse scroll wheel work too.
A frosted chevron at an end means there are more tiles in that direction. You can adjust all three scrolling speeds in Settings. See Can I change the curtain's speed?