The whdata, whgdata, and whxdata folders contain the .htm,
.js, and .xml files that store all the data for the left pane (TOC,
Index, Search, Glossary).
However, these files are not static; as you add data, RH will
rebalance their contents into other sequentially numbered files to
absorb new data as size limits are exceeded. Keeping these files
smaller helps in improving performance.