Thank you John!!
Using the current_filter() i’ve founded was i was doing wrong. The right one is:
impostazioni-fashion_page_gestione-livelli-abbonamento
Basically it doesn’t use the “menu_slug” but use “menu_title”. (Maybe is my fault because i’ve used two different names).
Anyway thank you very much!

Hi John!
Thank you for your reply, it is exactly what i was looking for. I’ve got a small question. If i use it on top level page, it works perfectly, but i can’t make it works with sub option page.
My code is:
if( function_exists('acf_add_options_page') ) {
acf_add_options_page(array(
'page_title' => 'Impostazioni',
'menu_title' => 'Impostazioni',
'menu_slug' => 'theme-trends-settings',
'capability' => 'edit_posts',
'redirect' => false
));
acf_add_options_sub_page(array(
'page_title' => 'Forms',
'menu_title' => 'Forms',
'parent_slug' => 'theme-trends-settings',
));
acf_add_options_sub_page(array(
'page_title' => 'Gestione livelli abbonamenti',
'menu_title' => 'Gestione livelli abbonamenti',
'parent_slug' => 'theme-trends-settings',
'menu_slug' => 'gestione-livelli-abbonamento'
));
add_action('theme-trends-settings_page_gestione-livelli-abbonamento', 'before_acf_options_page', 1);
function before_acf_options_page() {}
add_action('theme-trends-settings_page_gestione-livelli-abbonamento', 'after_acf_options_page', 20);
function after_acf_options_page() {}
What i’m doing wrong?
Thank you
Founded the solution in ACF documentation.
$medias = [23556,23586,23635];
update_field('gallery', $medias, $post_id);