I use plasma vaults! Its great for homework folders and tax information!
One frustration with vaults though is that theres no clean way to make a portable vault on a USB stick or backed up to a cloud provider (nextcloud, google drive, etc) without digging into weird dot-folder paths and manually entering links to these in a text config file. FUSE-style integration would be rad.
EDIT: The primary use case for this would be to be able to carry sensitive information around like PII, tax, password vaults, family photos, documents, and so on, in such a way that you always have it on you (like on a keychain) or backed up elsewhere, and would be especially useful in cases of disaster - but if you drop and lose it somewhere, a malicious actor doesnt suddenly have your data.