@impermanen_
Very quick-n-dirty (20 min) PNG export, no cleanup/perfecting done. This app makes SVG (vector graphic) files natively, which don’t get “jaggy” when printed large.
Never do coloring book stuff myself (not since the early ‘70s), so I dunno how much detail is desired in the line work. Lemme know if this is at all in the ballpark. No offense will be taken if the answer is, “No, not like that.” LOL
But if this is approaching useful, I can put real time into tidying.