Here is the answer
<?php
add_filter('acf/settings/save_json', 'my_acf_json_save_point');
function my_acf_json_save_point( $path ) {
// update path
$path = dirname( __FILE__ ) . '/acf-json';
// return
return $path;
}
add_filter('acf/settings/load_json', 'my_acf_json_load_point');
function my_acf_json_load_point( $paths ) {
// remove original path (optional)
unset($paths[0]);
// append path
$paths[] = dirname( __FILE__ ) . '/acf-json';
// return
return $paths;
}