This takes our standard topic list navigation and puts it into a sticky sidebar (as long as your browser is wider than 768px). You also have the option in the settings to show the sidebar on the right.
We’ve talked about this layout a little bit on Meta previously (Proposing a left-aligned slide out hamburger menu), and I was curious to see what it would be like to simply move our existing navigation to a sidebar.
Keep in mind that since this is a drastic layout change, this component may not be immediately compatible with other themes.
I think the topic list sidebar should appear in tag lists as well, so when you view say subfolder the sidebar will remain consistent across all pages and serve to be more useful. This will be a very neat feature.