Missing reference field for journal articles

For the reference type “Journal Article” consists of two fields:

Volume

Issue

Sometimes a publisher wants to add extra content to a journal without having an extra issue. So they add a part sometimes called “Supplement”, other times “Part 1” etc

Typically this is the case with accounting, anthropology, psychology, sociology

So we urgently need a third field which can be left blank when not used called “Part”

Please advise when this will be implemented. If you need further details please advise