Forse intendi qualcosa del genere ?
codice:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<form action="#" method="post">
<input type="text" id="cdSezi" value="REF.">
<select id="idtpCircolazione" name="tpCircolazione">
<option value="D">DISTRIBUTORE</option>
<option value="I">INTERNA</option>
<option value="L">LIBERA</option>
<option value="N">NO</option>
<option value="O">Disponibile online</option>
<option value="Y">Escluso ILL/ISS a tempo</option>
<option value="Z">Escluso ILL/ISS definitivo</option>
</select>
</form>
<script>
const select = document.getElementById('idtpCircolazione')
const ref = document.getElementById('cdSezi')
const optionI = Array
.from(select.children)
.filter(option => option.value.includes('I'))
function controllaMovimentiInve() {
ref.value == 'REF.'
? optionI[0].setAttribute('selected', '')
: optionI[0].removeAttribute('selected')
}
controllaMovimentiInve()
ref.addEventListener('input', controllaMovimentiInve)
</script>
</body>
</html>