The menu command Insert provides several options most of which are discussed elsewhere. Some that aren’t are
Horizontal line. Inserts a horizontal line across the width of a block at the point selected. This doesn’t have to be in the simple default style you can define a class and apply it to customise the line.
HTML. Allows you to insert some hand-coded HTML code at any point on a page. (If you want to add code in the HEAD area you’ll have to use 'Source' view instead.)
If you wish to insert HTML into your page this is probably the safest way to do so. While you can still mistakes in the code Nvu will carry out some checks and ensure that the result is valid HTML (whether or not what you intended). Editing in Source view (see section 3.15) can cause massive corruption of your page.
Characters and symbols. Provides a wide range of characters not readily available from the keyboard including accented and copyright.
Table of contents.
Inserts a table of
contents, based on heading styles which can be selected. The table
entries are linked to the corresponding headings.
Smart Widgets. Provides a small selection of novelties (A calendar and ‘Made with Nvu’ – If you’re proud of your design and that fact that Nvu helped you why not use it.)
Break below image. If you have an image aligned right or left (with text wrapping around it) this command breaks the wrap at the point selected the text continuing below the image.
Comments are commonly used by coders in order to improve maintainability of code. Comments do not appear on a page. Nvu helpfully displays an exclamation mark in viewing modes other than preview which when hovered over reveals the content of the comment.

Nvu User Guide - Based on Nvu version 0.9 - Updated 01-Apr-2005