Experimental feature: table of contents block. The ToC block can derive an interactive table of contents from the headers in your document. This is useful enough to release, but it's a little buggy. The issues can all be worked around while I fix them-- navigating away and coming back does the trick.
Known issues:
Doesn't re-render when updated in a dialog occupying the same screen.
Leaves trash DOM elements on the screen if deleted in a selection.
Clicking on the command, rather than hitting enter, leaves the command text on the screen.
Also, it's my birthday! Wew!