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