the model is designed as follows
const RegistrationSheet = mongoose.model("RegistrationSheet", new Schema({
  doctorId: String,
  today: {
    time: String,
    date: {
      morning: [
        {
          number:Number,          
          patient: String
        }
      ],
      afternoon: [
        {
          number:Number,          
          patient: String
        }
      ]
    }
  },
  tomorrow: {
    time: String,
    date: {
      morning: [
        {
          number:Number,
          patient: String
        }
      ],
      afternoon: [
        {
          number:Number,          
          patient: String
        }
      ]
    }
  },
  afterTomorrow: {
    time: String,
    date: {
      morning: [
        {
          number:Number,          
          patient: String
        }
      ],
      afternoon: [
        {
          number:Number,          
          patient: String
        }
      ]
    }
  }
})) now I want to insert a piece of data into the morning of today"s date. 
 according to the previous doctorId 
