Michael Bauer [MVP - Outlook] wrote:

To merge the categories A and B into C: Switch to a table view that
displays all of the items and group by categories. Select one item
and create the new category C. Now select all items of category A,
display the Categories dialog, check category C and uncheck category
A. Do the same with the category B items.

See, I would have intrepreted "merging two caletgories" to mean "make 'A and
B' a single category".
--
Brian Tillman