With the merging functionnality, you can add to one catalog all disks (with categories and descriptions) of another catalog
To do this you will have to :
Open the first catalog file (the one to copy disks from)
Click on : File->Merge ... choose the second catalog file (the one to add disks to)
The current catalog is know the second one. The first one is unmodified.
To save the merge, save the current catalog
Categories and descriptions are also merged. Only distinct categories and descriptions are added.