I don't know why o doesn't work in place of the parentheses. I also wanted to replace ↑ and N with a range of some sort, but afaict there's no [1..n] builtin, and incrementing would require another set of parentheses
If you want to use d+d← without parentheses, you need to compose all four functions (o only composes two like (.)).. So either you use odo+od← which is longer or use the ö built-in to compose 4 functions in one go: