Custom fields in WooCommerce Wholesale Lead Capture let you add custom fields of many different types to your wholesale customer registration form.
Dropdown fields, in particular, are very powerful for forcing users to select from pre-defined options.
If you wish you can also add a “— Please Select —” which will have no value and therefore not pass validation if you mark the field required.
Add this option to your custom dropdown add your dropdown field via the custom fields interface in the settings (WooCommerce->Settings, Wholesale Lead, Custom Fields sub page) as per normal.
Then, add a new option to the list, giving it a display name such as “— Please Select —” while leaving the Option Value field empty.
Finally, move the field to the top of the list.
If you want to force users to select one of the options, ensure you have the “Required” setting enabled.
On the front end you will see your field like so (validation failure is shown):