I needed to hide the first value in my dropdown list only on one page because it was not applicable. I used this on DIVI with Formidable PRO and it worked great. I just put the CSS in the Custom CSS. I wanted to hide the first value. I also wanted to do it for a specific page.
.page-id-7140 .chosen-results li.active-result:nth-child(n+1):nth-child(-n+1) {
display: none !important;}
I sourced the information from post #304410 on https://connections-pro.com/support/topic/hide-categories-via-css