Remove composer & artist from %work%

For an easy use of my classical collection in Foobar, I created a %work% tag (like an "opus"), because many CDs contain several works ; I wanted to compare them easily, and it ;-).
So I first filled an initial work tag, then added the composer and the artist (or conductor), so now my new %work% field was composed this way : %composer% / initial work - %artist%
e.g. : Schumann / Davidsbündlertänze, Op. 6 - Laloum A.
But this personal recipe is not convenient with other readers, as in my car or in Volumio.
They can display the album, the title, but not the work.
So I would like to clean this %work% tag. get only the middle :
Davidsbündlertänze, Op. 6
Ultimately I will easily merge the work in the title, with the Tag->tag converter, and will get a relatively short and readable title on small screens, like this :
Davidsbündlertänze, Op. 6 - I. Lebhaft
(the composer and artist names being already displayed in the album name)

I need a batch command, for it would be applied to ...2TB of flac files.
(15 years of wrong tagging !)
Many thanks by advance,

You could use an action of the type "Guess value"
Source: %work%
Target: %composer% / %work% - %artist%
This will update also the field COMPOSER and ARTIST
If that is not the desired way and only the work part should be left over:
Target: %dummy% / %work% - %dummy%

Thanks for the suggestion.