For more complicated patterns, 3x3 is too many copies to at least visualize how something tiles. If it's a brick, 1x2 or 2x1 would even be helpful, but at least 2x2 so you can see all seams.

Please create an option to disable the preview thumbnail in pattern editing mode. The thumbnail redraws for every edit, so more complicated patterns not only have to redraw on screen, but also create a miniature version. Hopefully those previews are images but if not, may be causing further issues when scaling down vectors.

Would it be possible to make a draft quality preview like InDesign? Presumably a different process, just throwing out options.