The category data is saved in the same data base used for smart content. A few releases back, DAZ changed from using the old Valentina data base to using PostgreSQL. At the time PostgreSQL was released there was a conversion utility that was a (free) product in DIM. It did not really install anything, but it created a PostgreSQL data base from your Valentina data base.

For a few bug fix releases DAZ Studio supported both data bases and you could pick which you wanted to run. PostgreSQL is faster and more stable than the old Valentina data base, but with the 4.8 release DAZ seems to be phasing out support for the Valentina data base.  It is apparently no longer shipped with DAZ Studio, although they say it is still supported. 

My guess is your categories are in the Valentina data base, but you 4.8 DAZ Studio is using PostgreSQL or else something went wrong in the conversion between Valentina and PostgreSQL.  

Did you install DAZ Studio 4.8 using DIM?  Did you install a product like Valentina to PostgreSQL data base conversion?