In a medium bowl, whisk together the flour, baking soda, cinnamon, and salt. In a large bowl, vigoriously whisk the melted butter and sugars until the mixture takes on a lighter consistency and slightly pale color. Add the egg and vanilla extract until mix until combined. Using a rubber spatula, fold in the flour mixture followed by the rolled oats, dried cherries, coconut chips, and walnuts. Cover the bowl and chill, at least 1 hour.