This infuriates me. There are so many problems I run into, day-to-day even, which could be readily solved if files/folders just had a stringly-typed key-value metadata store of arbitrary size which was portable-ish across file systems. Heck, even just one bytes field I can dump json or some serde into, that doesn't impinge on the actual file bytestream. xattr is close but no cigar.

Instead you either need sidecar files, archives, or custom binary formats.

It's as if the posix filesystem abstraction crystallized a bit too soon (same like tcp/ip)