Here is the trick which is not really one, I was looking too far :
in /admin/customers.php
around line 1212
Code:
if (!$emp_result->EOF && ($_SESSION['admin_id'] == EMP_LOGIN_ADMIN_ID || $emp_result->fields['admin_profile'] == EMP_LOGIN_ADMIN_PROFILE_ID) ) { /*v1.7.0c*/
should be
Code:
if (!$emp_result->EOF && ( $_SESSION['admin_id'] == EMP_LOGIN_ADMIN_ID || in_array ($emp_result->fields['admin_profile'], explode (',', EMP_LOGIN_ADMIN_PROFILE_ID)) )) {
And now my cashier has the button and everything is fine.