This is crazily sad non-invasive (without embedding into the file body) tagging is not standardized across OSes and file systems. The only system to support tag

This is crazily sad non-invasive (without embedding into the file body) tagging is not standardized across OSes and file systems. The only system to support tags I know is KDE/Dolphin/Baloo, outside KDE tagging seemingly is supported only by a handful of incompatible 3-rd party apps. Sadly I don't expect much progress to happen in this area. Almost nobody cares about storing and organizing of files locally nowadays. I hope it is going to be done some day or later (there isn't much to do: just standardize some xattrs and something like RDF schema to be used in an alternative FS stream + add support for these to the standard file management and search tools, this is orders of magnitude easier than implementing a new FS) but probably not soon - it would be a huge luck to get any resources allocated to this.