grouping list of objects in the help system

Dear list,

I've noticed for some packages the Index file in the help system has a
single list of objects (arranged alphabetically), while for other
packages this list is offered separately by letters... presumably when
the number of help objects is high.

Is there a way to manually split the help objects into categories?

For example, I would like to have an alphabetic order for the group
"datasets" and another alphabetical order for the group "functions".

Needless to say that I've tried to read everything I could on this
topic (especially "Writing R Extensions"), even looked closely on
different package sources, but I haven't noticed anything special.

Thanks,
Adrian

Adrian Dusa
University of Bucharest
Romanian Social Data Archive
Sos. Panduri nr.90
050663 Bucharest sector 5
Romania