G_Sheets_Remove_Excess_Columns_and_Rows.js

function deleteExtraColsAndRows() {
  var ss = SpreadsheetApp.getActiveSheet()
  
  //Columns
  var lastCol = ss.getLastColumn();
  var endc = ss.getMaxColumns();
  try{
    ss.deleteColumns(lastCol+1, endc-lastCol);
  }catch(e){Logger.log('col error: '+e)}
  
  //Rows
  var lastRow = ss.getLastRow();
  var endr = ss.getMaxRows();
  try{
    ss.deleteRows(lastRow+1,endr-lastRow);
    ss.insertRowsAfter(lastRow, 10);
  }catch(e){Logger.log('row error: '+e)}
}