endnotes.heading.groups — Display the endnotes by groups
<xsl:param name="endnotes.heading.groups"/>
In the endnote section, the notes are grouped according to the level
defined by the elements listed in this parameter. Each group has a heading
that references the element that contains these notes.
By default, dblatex can group per chapter or per
part. For more details
see the section called “Grouping Endnotes”.