Hi @Jan Martin, I manage the Help Center here at Miro. First of all, thank you for your nice comment about our Help Center, that’s very kind of you! We take great pride in our work so that feedback is always appreciated.

To answer your question: we use Zendesk Guide for the main platform, along with some custom javascript and CSS for styling. We also use a third-party plugin from Lotus Themes to create the accordions and tabs you see in certain articles. 

Hope this helps, but feel free to send any other questions my way!