Preheat oven to 325 degrees. In a food processor, combine cookies, walnuts, sugar, and salt; process until fine crumbs form. With machine running, slowly pour butter through feed tube and process until mixture resembles wet sand. Press crumbs in bottom and up side of a 9-inch pie plate. Bake until crust is deep golden brown and fragrant, 25 minutes (check crust halfway through; if puffed, flatten with the bottom of a measuring cup). Let cool completely in pie plate on a wire rack.
Place 3 tablespoons cold water in a small bowl. Sprinkle gelatin on top and let stand 5 minutes. In a small saucepan, combine cream, honey, and 1/4 teaspoon salt; bring to a simmer over medium. Whisk in gelatin mixture until completely dissolved. In a large bowl, whisk together yogurt and vanilla until completely smooth. Add cream mixture to bowl and whisk gently to combine. Pour filling into cooled crust and refrigerate until chilled and completely set, about 2 hours (or wrap tightly with plastic and refrigerate, up to 2 days).
In a small saucepan, combine dried plums, sugar, orange zest, 1/2 teaspoon salt, and 1/2 cup water. Bring to a gentle simmer and cook until dried plums are soft and liquid is syrupy, 20 minutes. Let cool. To serve, spoon topping over pie.
Dried cherries, peaches, or cranberries would also work nicely for the topping.