View all categories and register a new subcategory

It would be good to have an overview of all existing categories and subcategories, so that when categorizing an entry, it is easier to select the category instead of having to search for it in the dropdown menu.

It would also be good to be able to register new subcategories, for example, within "Housing" and "Health." From what I tested when registering a category, it appears as "global" within income/expenses.