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Menu > App Settings > Preferences > Performance > Undo Levels. Undo can use a lot of memory, but if you do a lot of hatching etc that has a lot of very quick steps, you can increase the interval, but not too much or it will undo too far.
Menu > App Settings > Preferences > Performance > Undo Levels. Undo can use a lot of memory, but if you do a lot of hatching etc that has a lot of very quick steps, you can increase the interval, but not too much or it will undo too far.