It would be much better if you could update the layout for ALL pages, rather than just some pages using the Manage Layouts. For example, I don't see anywhere to edit checkout pages or custom web pages. It would be less confusing and less time consuming to be able to do everything in one place, rather than having to do some of it here and the rest of it directly in Visual Studio.
This is idea is currently under review for a future release. Visual Studio should not be a requirement to edit any page in AbleCommerce. It might take some work, but we are looking it over and will make a decision within the next few weeks.