Hi @mathieu I have the same issue, did you find a solution for that?
here is the code I use
if(function_exists(“register_field_group”))
{
register_field_group(array (
‘id’ => ‘acf_categories-settings’,
‘title’ => ‘Categories settings’,
‘fields’ => array (
array (
‘key’ => ‘field_55cd9d1bdb108’,
‘label’ => ‘Featured Image’,
‘name’ => ‘categories_featured_image’,
‘type’ => ‘image’,
‘save_format’ => ‘object’,
‘preview_size’ => ‘header’,
‘library’ => ‘all’,
),
),
‘location’ => array (
array (
array (
‘param’ => ‘ef_taxonomy’,
‘operator’ => ‘==’,
‘value’ => ‘category’,
‘order_no’ => 0,
‘group_no’ => 0,
),
),
),
‘options’ => array (
‘position’ => ‘normal’,
‘layout’ => ‘default’,
‘hide_on_screen’ => array (
),
),
‘menu_order’ => 0,
));
}