The geometric Satake correspondence provides a beautiful geometric description of the representations of reductive groups, using the affine Grassmannian. In order to categorify this description, we use truncated shifted Yangians which quantize slices in the affine Grassmannian. Last year, we proved that category O for a truncated shifted Yangian is equivalent to a category of modules for a Khovanov-Lauda-Rouquier-Webster algebra. In this way, we obtain a categorical action on category Os for truncated shifted Yangians.