By now we only have promo as sub-format in release groups.
Here’s an example where a CD release is accompanied by a promo CD.
where I put the info in the annotation.
Afaik this also happens with vinyl releases + bonus CD/EP/single.
Maybe we could have this as sub-format in the medium-section too.
If this was one release, it was probably promotional altogether. Or was it sold to the public, including a disc labelled “not for sale”? I don’t think a partial promotional release is possible.
I would duplicate the edition without the additional CD and make a 2CD release for this one, like that additional “Leaving” bonus disc in stand alone cardboard sleeve.
My problem: I don’t have this 
Good solution, I think. On discogs there’s also a 10-track release
https://www.discogs.com/release/8099734-EST-EST-Live-95
In my collection there’s only this: https://www.discogs.com/release/16112467-Esbjörn-Svensson-Trio-EST-Live not on MB (yet).
