On the an item's edit view, select the Structure tab, then click Edit Structure

The editor will open in a modal window overlaying the rest of the page.

The elements are:

top waveform view

This represents, contains the

bottom waveform view

Each heading and section will be represented by a block. Indents indicate nesting in the hierarchy

Headings are labels.

Timespans are labeled ranges of time that turn into hyperlinks in the