https://github.com/metabrainz/picard/pull/2600 looks good, but while testing I notice another issue: using drag'n'drop to re-order values works, but if you edit a tag, select another one, and come back the order isn't always preserved. Using your example, create a new tag, add a,b,c values, re-order using drag'n'drop, switch to another tag, and come back