Add Prefix to Search & Filter Option Labels

functions.php

<?php
// Add prefix to Search & Filter Option Labels
function filter_input_object($input_object, $sfid) {
    //* Exclude all non-targeted fields
    if(($input_object['name']!='_sft_field_name')) {
        return $input_object;
    }

    //* Exclude fields without options
    if(!isset($input_object['options'])) {
        return $input_object;
    }
    
    // Add prefix to each option
    foreach($input_object['options'] as $option) {
        $option->label = "Prefix Text ".$option->label;
    }
    
    return $input_object;
}
add_filter('sf_input_object_pre', 'filter_input_object', 10, 2);