[{"_id":ObjectId("6527c64e539e51befb0db39c"),"category":"fruits","dataType":"string","isList":true,"item":[null,"mango","banana","kiwi","orange",null,"watermelon"]}]

db.collection.update({_id:ObjectId("6527c64e539e51befb0db39c")},[{"$set":{"item":{"$concatArrays":[{"$slice":["$item",3]},{"$slice":["$item",4,{"$size":"$item"}]}]}}}])