The big disadvantage of the solution you present in the screenshot is that the information is hidden in the gutter. And permanent visibility of the information is not really ideal.
Nevertheless, it is actually difficult to recognise the hierarchy at first glance, especially with the headings from level 4 to 6. In fact, it’s impossible to see it unless you place the cursor in the heading.
I once suggested autonumbering on a per note level for this purpose which I actually consider as perfect. Different coloured headings would also be a possible solution. Which solution would actually be the best for bear, I trust the developers. They would come up with their own idea, provided of course that they recognise the problem