1. When setting up a new backup job, there should be a way to enter something which you would see in the "Backup Set Description:" field while looking at a backup set's properties after the job completed. (Perhaps the "description" field that already exists in the job definition)?
After a lengthy support case with Symantec I've been told there's no way to do this any more. Which is a shame because sometimes it's the only way to tell that two backup sets are replicas of the same thing.
This used to exist in older versions of Backup Exec, and bizarrely, existing jobs that were converted over from older versions of the software still write out description information. Somehow. But there is apparently no way to do it for a new job.
2. There should be some way to enter description data after the fact and preserve it. There is already an analogous functionality in media (i.e. tape cartridge) properties. That screen has a Media Description field and a Yes/No dropdown to preserve the description. Something like that should exist for backup sets.