Hide Categories

You can remove category field by adding following code in your theme functions.php or by creating a new plugin and pasting this code there.

add_filter("adverts_form_load", "remove_category_dropdown");
function remove_category_dropdown( $form ) {
    if($form["name"] != "advert") {
        return $form;
    }
    foreach($form["field"] as $k => $field) {
        if($field["name"] == "advert_category") {
            unset($form["field"][$k]);
        }
    }
    return $form;
}

Is there a way to hide a specific category from the frontend? For example, if we created a category called “featured”, and manually assigned paid posts to that category?

Currently the best you could do (without some more advanced custom programming) is add following code in your theme CSS file

.advert_category-100 { display: none }

This will hide category with ID 100 from the list in dropdown, but note that more advanced users will still be able to ‘hack’ it and select this category.