Hi!
I want put button “Select All” to checkbox field. The problem is for Categories don’t exist. Is possible add it? I was thinking about populate categories in another field type but i can’t populate it!
For Taxonomies, i’m populating this way:
add_filter('gform_pre_render_1', 'lc_populate_member_option');
function lc_populate_member_option($form){
    $terms = get_terms( array(
        'taxonomy' => 'experiencias',
        'hide_empty' => false,
        'orderby'   =>'title',
        'order'   =>'ASC',
    ) );
    $items = array();
    foreach($terms as $term)
        $items[] = array(
           "value" => $term->slug, 
           "text" =>  $term->name
      );
    foreach($form["fields"] as &$field)
        if($field["id"] == 35){
            $field["type"] = "Experiencias";
            $field["choices"] = $items;
        }
    return $form;
}