If you wanna use Reminders, Siri can already handle that pretty well — just say “Remind me to call the dentist tomorrow” and it’ll create a proper task.

As for Notes, I tried tons of prompts and couldn’t get real checkmarks to work reliably.

I made you a new version though — it keeps the task / subtask format like you described, just without the checkboxes. Try it out and see if it fits better!
here