When you add one category with subcategories it shows up blank.
I understand that your reasoning is that if you only add one category with subcategories you should be using only main categories from the beginning.
1) BUT, sometimes you want to use a category more than once for different products. In some cases, the category will be used with other categories and in other cases it will be used alone. This option is currently not possible.
2) Once you have created a category with subcategories you cannot select the subcategories anymore.
3) Adding one category with subcategories also helps overcome a major problem that I have with categories. There is no way to write a note to label sizes. For example, if I have a category for A4 and one for US letter the only way that I can label that is to create a main category with subcategories.
Please enable us to select one category only with subcategories.
I think that it should be set so that when you have only one category with subcategories you see only the subcategories. Right now it just shows up blank.