[{_id:1,"add":[{"id":"1","name":"wk1","iconFile":"icon.png","elements":[[{"id":"2","name":"element2","link":"https","elements":[{"id":"1","name":"element1","link":"https:"}]}],[{"id":"3","name":"element3","link":"https://","elements":[{"id":"4","name":"w","link":"http:/"}]}],[{"id":"3","name":"element3","link":"https://","elements":[{"id":"4","name":"w","link":"http://"}]},{"id":"3","name":"element3","link":"https://","elements":[{"id":"4","name":"w","link":"http://www."}]}],]},]}]

db.collection.update({_id:1,"add.id":"1"},{$push:{"add.$[].elements":{id:"3",name:"a",link:""}}})