Is It Possible To Create Categories for an Alphabetized List?

In a Numbers 6.0 file, I keep a list of over 1000 books, CDs, and DVDs. The list is alphabetized. Is it possible to create a Category for items whose titles begin with “A”, and on through the rest of the alphabet so that I can collapse any letter group that I don’t want to browse through? I don’t see this in the options, so I wondered if I should create a column and use a formula somehow to read the first letter of the title and then use that column to create Categories? I may be overthinking this, so I thought I would ask. Thanks.
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Darrell Curtis