I know what it does. I wanted to know what you were trying to do.It helps organize your backups, rename them in a format you prefer, etc.
I mainly need it because I have no idea what versions these files are and the "v0, v65536," etc version number naming scheme Nintendo uses is bunk.
Switch Backup Manager might still work with an updated keys file and versionlist file, but I'm not sure. I haven't used it in ages.
NSC_Builder might also do what you're wanting. I'm not sure. I keep very few NSP files on my computer and mostly use Tinfoil shops like HBG, etc., not counting the occasional early release XCI.