I have an app script that imports CSV files to columns A:E. The problem I have is that if I add any data to say Column H, then my app script starts the import below that data instead of below the last row of data in the actual columns that I am importing into. I need the script to only judge the data in the first 4 columns.
I tried range = sheet.getRange(2,1,sheet.getLastRow())
Here is the code I am using.

function writeDataToSheet(data) {
    const ss = SpreadsheetApp.getActiveSpreadsheet();
    const sheet = ss.getSheetByName("Import");
    //const range = sheet.getRange(sheet.getLastRow()+1,1,data.length,data[0].length).setValues(data);
    const range = sheet.getRange(2,1, sheet.getLastRow()+1, data.length, data[0].length).setValues(data);
    return sheet.getName();
  }

>Solution :

Modification points:

• In the case of const range = sheet.getRange(2,1, sheet.getLastRow()+1, data.length, data[0].length).setValues(data);, 5 arguments are used in the method of getRange. In this case, 4 arguments are used.
• In your script, it seems that range is not used.
• In your situation, how about checking the last row of the column "A"?

When these points are reflected in your script, how about the following modification?

Modified script:

function writeDataToSheet(data) {
  // ref: https://stackoverflow.com/a/44563639
  Object.prototype.get1stNonEmptyRowFromBottom = function (columnNumber, offsetRow = 1) {
    const search = this.getRange(offsetRow, columnNumber, this.getMaxRows()).createTextFinder(".").useRegularExpression(true).findPrevious();
    return search ? search.getRow() + 1 : offsetRow;
  };
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  const sheet = ss.getSheetByName("Import");
  sheet.getRange(sheet.get1stNonEmptyRowFromBottom(1), 1, data.length, data[0].length).setValues(data);
  return sheet.getName();
}

• By this modification, the values of data is put from the next row of the last row of column "A".