You can undo all of any changes that you have made by clicking the advanced button resetting to the default mappings. This is going to set all mappings back to the factory default. Any mappings that you have manually added and any advanced customization that you have made to a particular mapping will be lost. With that in mind, before you choose reset mapping, it would be a best practice to choose export all, to save your customizations to a file. This file contains all current mappings.