Hey @Sander van der Veen, thanks for reaching out!
What you’re seeing is expected right now. We’re slowly rolling out the new navigation bar to users in Figma Design. While we’re rolling this out, users might see different versions of the Figma UI until we’ve fully rolled out the new navigation bar.!-->
The new sidebar (with things like variables more easily accessible) will become available as the rollout continues, there isn’t a way to manually switch it on just yet.