To create the fields, I use the ACF Builder library.
I can’t set up saving these fields to the acf-json folder. The problem is that the fields were created before the acf-json folder.
add_filter('acf/settings/save_json', function() {
return get_template_directory() . '/acf-json';
});
add_filter('acf/settings/load_json', function($paths) {
unset($paths[0]);
$paths[] = get_template_directory() . '/acf-json';
return $paths;
});