How do you post items in a marketplace subcategory

When adding subcategories to the marketplace there does not seem to be a way to easily post items into the subcategories if the parent category is not a container.

clicking the parent category goes to the form for that category. It would be great if a parent category has subcategories added that there be an option to see the subcategories, maybe a form field or something to select subcategories under the parent

Also trying to change a parent category from a regular category to a container results in an error

 1054 Unknown column 'Array' in 'where clause' 

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