Allow disk catalogs to be updated with new files
Often files get updated on disks - changes to files, new files, or even removed files. It would be very useful if instead of only being able to make a new catalog for that disk, that it could instead update the original catalog, adding the new or changed files or removing any files that have been removed from the disk.
It would also save hard drive space.
You can already do that. Make sure you have Check Duplicates checked in View→Options. If you scan the disk again after turning it on it will show as a duplicate disk. You can update existing disk or choose to create the new disk on duplicate disk dialog.