Navigation sidebar not expanding sub-links automatically

The "Side navigation" UIKit component is currently powered by the "Primary menu" Drupal menu. This menu also powers the "Primary navigation" UIKit component (in the Header component).

The "Show as expanded" checkbox on each menu item should be respected in the "Primary menu" in cases where sub-trees should not be visible.
This issue is about whether this checkbox should be respected or ignored completely in the "Side navigation" component, because, bey definition, the side navigation is expected to allow to drill-down to the menu item that points to the current page (if the page is in the menu, of course).

The solution here is to keep respecting individual values of "Show as expanded", but override them all if "Expand all menu links" item is provided in the block.

For this to work, we need to get the value of the "Expand all menu links" on the menu block and pass it to the Drupal's preprocessing of the menu items to mark them all as expanded.

Verified and tested on 1.x-dev

Testing Results:
1. Upon selecting 'Expand all menu links' checkbox in the "Side Navigation" block, all sub-menu items are visible in the side navigation - PASS
2. Upon unselecting 'Expand all menu links' checkbox in the "Side Navigation" block, individual values of "Show as expanded" is respected - PASS

Screenshots:
Selecting 'Expand all menu links' checkbox

Unselecting 'Expand all menu links' checkbox

alex.skrypnyk → credited joshua1234511 → .

We have identified that we also need to apply the same behaviour to the Mobile navigation.

Verified and tested on 1.x-dev

Testing Results:
1. When ‘Show as expanded’ is unchecked for L1 / L2 menus, the child menu items are not displayed on mobile. - PASS
2. Works fine on desktop - PASS

Screenshots:

‘Show as expanded’ is unchecked

The child menu items are not displayed

Implemented, tested, merged and will be released in 1.7.

Automatically closed - issue fixed for 2 weeks with no activity.