[{_id:1,items:[{value:"abc",other:"other1"},{value:"def",other:"other2"}],other:"other"}]

db.collection.update({},[{"$addFields":{"items":{"$map":{"input":"$items","as":"i","in":{values:["$$i.value"],value:"$$i.value",other:"$$i.other"}}}}}],{multi:true})