Drupal 8 is becoming more and more API-first based. This means a lot of imports and exports of data will be done. A thing you might face here, is that the updating of entity reference fields is a bit tricky. Here I'll show you how it is done.
I had this use case in my theme, where I wanted to expose a bunch of settings to my page.html.twig. Typical things would be social media links. Here is how I looped over config file values, preventing me to write a lot of lines: