Fill nested object in array mongoose with Schema

I've tried in so many ways to fill an array of objects but I can't find a solution, the arrays know that by default they're always empty, but I can't find a way to populate this complex array

const mongoose = require('mongoose');
// Fasi
const DateSchema = { type: Date, default: new Date(false) };
const NumberSchema = { type: Number, default: 1 };
const StringSchema = { type: String, default: '' };

const CustomSchema = {
  tempoaSchedaInOre: DateSchema,
  tempoTotaleInOre: DateSchema,
  tempoTotaleInMinuti: NumberSchema,
};
// End Fasi

const preventiviSchema = mongoose.Schema({
  data: {
    type: Date,
    default: Date.now,
  },
  fase: {
    type: [
      {
        controlloMaterialeSmd: CustomSchema,
        equipaggiamentoSerig: CustomSchema,
        equipaggiamentoPeP: CustomSchema,
      },
    ],
  },
});

mongoose.model('preventivi', preventiviSchema);

and generate this:

{
  "data": {
    "$date": "2020-12-24T11:02:45.322Z"
  },
  "fase": [],
  "__v": 0
}

My intent is to generate an array with all the elements directly in the Schema,

Thanks to all