For the additional library to work correctly, you will need to enable "Show as expanded" on all menu items that have submenus (children).

show as expanded on menu item screenshot

 

Once applied to the page or theme, aside menus with submenus (children) will appear collapsed with an icon to open them and reveal the submenu example on in the aside menu item Components and screenshots below.

accordion menu collapsed
accordion menu collapsed
accordion menu open screenshot
accordion menu open