Hi Markus
We don’t have a quick way to do this. However, it shouldn’t be too technical either.
For each category, we have a link like this:
http://yourdomain.com/events/category/sports/
http://yourdomain.com/events/category/sports/list <- for list view, etc.
You could make a bulleted list (even in a rough draft of a post), link the category name to the corresponding display, and copy/paste that code (from the text tab in editor) into a text widget.
Let me know if that works for you.
Thanks
Courtney 🙂