HED are a part of BIDS and can be a way to give more precise metadata descriptions of stimuli and events. Originally used for triggers in EEG but extended to all modalities.
https://bids-specification.readthedocs.io/en/stable/99-appendices/03-hed.html
http://www.hedtags.org/hed-docs/
I suspect that this too could / should be "dumped" into bids-matlab (possibly by reusing the HED matlab code)
https://github.com/hed-standard