How to increase dropdown field border in Designer?

Why in the designer I can't change the border pixels on my dropdown menus. I click the drop down menu, it toogles the menu and raise the border px to 3 and doesn't change.

https://form.jotform.com/60527416898972

We would like to apologize for any inconvenience, can you try to add this CSS codes to your account instead, please?

.form-dropdown {

    border : 3px solid black !important;

}

You can add it through Designer

or by following the steps on this guide, How-to-Inject-Custom-CSS-Codes

Thank you.