Add a counter column to the print preview of the table view in your AppGini app

footer-extras.php

<script>
  $j(() => {
    // show row numbers in TVP of the following tables
    // CHANGE THE TABLE NAMES IN THE LINE BELOW TO MATCH YOUR APP
    const tables = ['customers', 'employees'],
          tn = AppGini.currentTableName();

    if(tables.indexOf(tn) < 0) return;
    if(!tn || !$j('#sendToPrinter').length) return;

    $j('tbody tr').each((i, e) => {
      $j(e).prepend(`<td>${i+1}</td>`)
    })

    $j('thead tr').prepend(`<th>#</th>`)
  })
</script>