How often do you add vignettes to photos? More commonly than applying a grungy filter, I bet, and yet it's all the way down the bottom of the list. It sounds weird to put everything in alphabetical order, because what if the tools you use most often are at the bottom of the list? I mean, that's why it's laid out like that, so the most commonly used tools are at the top, ready to go. Stop! I can already hear you muttering at me, and yes, I know Lightroom doesn't do this either. Snapseed's Tools panel is currently not in alphabetical order and would do better if it was customizable.
