For the gluten-free flour blend: In a large bowl, whisk together the rice flour, tapioca flour, potato starch, xanthan gum and salt.
For the cookies: Pulse 1/2 cup walnuts in a food processor until finely chopped. Set aside.
Preheat the oven to 325 degrees F and line a baking sheet with parchment paper. In the bowl of a stand mixer fitted with the paddle attachment, mix together the granulated sugar, baking powder, salt, honey, vanilla bean seeds and eggs with 2 2/3 cups gluten-free flour blend and the ground walnuts until combined. Add the figs and the remaining 1 cup whole walnuts and mix until combined.
Divide the dough into 2 equal pieces. Dust a piece of parchment paper with some granulated sugar, then use your palms to gently roll each piece of dough into a log about 2 1/2 inches wide; place both logs on the prepared baking sheet. Brush with the egg wash and sprinkle generously with sugar. Bake on the prepared baking sheet until golden and slightly firm to the touch, about 40 minutes; set the baking sheet on a wire rack and let cool completely. Lower the oven to 300 degrees F.
Using a serrated knife, slice the logs slightly on a diagonal into 1/2-inch pieces. Arrange the pieces on their flat bottoms (not cut sides) on the baking sheet, staggering their ends so that the cookies hold each other in place. Bake until crisp, about 20 minutes. Let cool completely on their baking sheet.
In a small bowl, whisk together the confectioners' sugar and maple syrup until smooth. Drizzle over the cooled cookies and let dry before serving.