Hi Simon, I've also watched Maya's TidyBlock demo and loved it! I think we have everything in Snap! to completely do the same thing, but I also believe that Maya's mutation demo actually uncovers a problematic assumption about how to work to data sets. As someone who's worked in "big data" for some years I was trained to never, ever mutate data in place, but to always make a new view and leave the original unchanged. Maya seems to update the view with whatever she adds to the script last. I agree that - some - programmatic control over table views would go a long way. But I'm also afraid that it would open a can of worms about what people - wrongly - expect that to do. Let me think about it!