Show categories in the folder menu

The new user categories are great, and work similarly to Gmail labels, which is welcome for those of us who've migrated away from Google. However, it's difficult to get an overview of your categories (can we suggest that OX just call them labels to distinguish from inbox categories?).

In just the same way as there's a My Folders section of the folder list, I'd like there to be a collapsible section called something like My Categories that lists your created categories with message counts just like the folders. It should probably be customisable whether these go above or below the existing My Folders entry.

For bonus points, interpreting category names with "/" in them as nesting would be really great - you could have a tree of categories so they don't all have to be visible at once. Alternatively, allow true nesting so that category 1 can be a child of category 2 and so on.