Preheat oven to 350°F. Line two rimless cookie sheets with parchment paper.
Whisk flour, baking powder, baking soda, and salt in a medium bowl.
In a large bowl, whisk sugar, melted butter, egg, egg yolk, and vanilla until smooth.
Stir in flour mixture until combined.
Fold in oats, walnuts, coconut, and chocolate chips.
Spray a 1/4-cup measuring cup with vegetable oil spray. Scoop level 1/4-cup portions of dough onto sheets, 8 per sheet, 2 1/2 inches apart.
Bake one sheet at a time for 15–17 minutes, rotating halfway, until edges are firm and golden.
Cool on the sheet for 5 minutes, then transfer to a wire rack to cool completely. Store in an airtight container for up to 3 days.
For make-ahead options: Refrigerate portioned dough for up to 2 days or freeze dough portions for up to 2 months and adjust baking time accordingly.