How to show all sub-categories articles?

Question

Choosing menu item type to "Category Blog,List All Categories, and Category List" would result all subcategories link not direct to all articles of sub-categories.

But I want to show directly the all articles of sub-categories.

main-category
   sub-categories
       cat-1
            article
            article
            .......
       cat-2
            article
            article
            .......
       cat-3
            article
            article
            .......

Now, how to show all articles of main-category?

Answer 1

In Menu Item Settings: Blog Layout -> Choose Include Subcategories "ALL"

UPDATE

FYI: This behavior can be set also globally for all Blog Layout Menu Items.
In Article Manager Options -> Blog / Featured Layouts Tab -> Include Subcategories.

Answer 2

first, find the column params in your database table ###_extensions which row name is com_content.

update the inner value in the JSON string, "show_subcategory_content":0 to "show_subcategory_content":1 that mean for 1 level subcategory support.
This is a global configuration.

If you just want one menu item to support that, find the item in table ###_menu and add "show_subcategory_content":1 in params which works.