Welcome to the forum. I believe that since you are creating that note without an extra tab afterwards (step 2), the note would not have that task as its parent. Like the following,
- This is a task
This note is not related to the task above
- This is another task
This note is related to the task above
To accomplish the proper inheritance, following the task after you are done typing your note, press tab once.
Next, since what you are asking is for the program to figure out what to do next without any other context on your workflow; the permutations to create automatic format for all the possibilities would be literally infinite. Fortunately, you could accomplish this very easily using something like TextExpander or KeyboardMaestro. You can create your own shortcut, and then just use it and have one of those programs enter two spaces in your list, and have the task ready to go next.
Again, welcome to the forum. If you have more questions, you are encouraged to ask again.