Hierarchical Viewer - How do make a custom order item in each level

Depending on what you are building, for example, if you are building a mega menu, you can use the NodeOrder (the position of the page in the content tree) as the OrderBy.

Using the Hierarchical or Universal Viewer it's not possible without some sort of custom query or code. Another option is a nested repeater which doesn't perform all that well but it's an option. This will allow you to set individual values for each nested repeater. Again, not something you'd want to do simply because of performance reasons but might get you moving in the right direction.