[{"data":{"buttons":[[{"text":"Button","url":"https://example.org"}],[{"text":"👍","callback_data":"like"},{"text":"👎","callback_data":"dislike"}]]}}]

db.collection.update({},[{$set:{"data.buttons":{$map:{input:"$data.buttons",in:{$map:{input:"$$this",in:{$cond:[{$eq:["$$this.callback_data","like"]},{$mergeObjects:["$$this",{text:"changed"}]},"$$this"]}}}}}}}],{multi:true})