Workflow: When looking up metadata on MusicBrainz and making a match, story the MBIDs associated with that match in the file's metadata.
The obvious and immediate use case for storing the matched MusicBrainz IDs would be easier look-ups for updated data on MusicBrainz, but a more far-sighted perspective is that these MBIDs could be used for looking up data from additional sources too. E.g., acoustic data (tonality/key, bpm, female/male/instrumental vocals, ...) from AcousticBrainz, listening data (what recordings are commonly played in relation to this recording) from ListenBrainz, etc. MetaBrainz itself has a handful of services that talk MBIDs, but a number of MetaBrainz' supporters also allow using MBIDs in interfacing with them: https://metabrainz.org/supporters - and a number of audio file players/taggers also have some level of MBID support, in case files from a Mixxx library were ever played outside of Mixxx… ;)
The MusicBrainz Picard website hosts a table of the de facto MBID-to-audio-tag mappings: https://picard.musicbrainz.org/docs/mappings/
Related to https:/
Implementation of this feature can be started independently.