Ah, so this isn’t standard behaviour? I don’t have the specs to hand but it’s a basic laptop from a few years ago, definitely underpowered in video editing terms. That said once I’ve scrolled along and all the thumbnails are loaded they all stay loaded and I can scroll around with no issues, so if it is throttled based on PC performance it seems like overkill to me. It’s the scrolling that takes time, not the thumbnail loading – it literally won’t load a single one until I scroll forward, but then loads the now-visible clips pretty much instantly.