Display child items main navigation I created child elements for the main navigation. I went into the block configuration and adjusted it to show up to three levels of sub menu's.

For Drupal 7 I know that I used Nice Menu's to get the menu working with child links. But it's not usable yet with Drupal 8.

I was wondering if there was another module or how I could get my Child Links to show up.
You have to go to the menu configuration and manually check "expanded" for each item that has children. This is really annoying since there used to be a checkbox right on the list of links so you could do it on a single page at once. Not anymore.