The tabs tag is a direct child of the tinderbox tag.
<tabs>[nested one or more <tab> tags]</tabs>
The tag takes no attributes and acts as a container for tab tags, of which there should always be at least one (by default new windows have 2 tabs). The tag holds a set of tags representing each of the tabs in the parent window.
This listing holds a list of all unique tabs across all windows in the document (some may appear in several windows).