You can have any card show up anywhere on any page.
By default, wagn is configured to use a Classic Layout that includes the *sidebar card on the right sidebar. You can simply edit that card to change the contents of the sidebar.
Note: the default views for cards included in the sidebar (or anywhere outside the main card) is naked, rather than the usual content.
(For the sidebar here on wagn.org we've also modified *css to style our sidebar's home buttons links to Download, Docs, etc.)