sheets.js

function CaptureNetWorth() {
  var USD_NW_COLUMN = 2;

  var destinationSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Daily NW');              
  // Get index of the last row in column A that doesn't have content
  var Avals = destinationSheet.getRange("A1:A").getValues();
  var lastRowIndex = Avals.filter(String).length;
  
  var newRowIndex = lastRowIndex + 1;
  
  insertDate(destinationSheet, 1, newRowIndex);
  getUSDCell().copyValuesToRange(destinationSheet, USD_NW_COLUMN, USD_NW_COLUMN, newRowIndex, newRowIndex);
}

function getUSDCell() {
   var sourceSheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName('Net Worth');
   var sourceTotalRef = "$A$1";
   var sourceCell = sourceSheet.getRange(sourceTotalRef);
  
   return sourceCell;
}

function insertDate(sheet, x, y) {
 // insert date
  function pad(number) {
      if (number < 10) {
        return '0' + number;
      }
      return number;
  }
  function fmt(date) {
      return date.getUTCFullYear() +
        '-' + pad(date.getUTCMonth() + 1) +
        '-' + pad(date.getUTCDate());
    };

  var d = new Date();  
  sheet.getRange(y, x).setValue(fmt(d));
}