no show scrollbars

Hello dear

NO SCROLLDOWN
I need add a longe list, but I can see the list is more and more long in the dropdown and no show a scrolldown for select a item

I think should be similar to the admin interfaz, and works similar (with similar CSS and with scrolldown)

NO AJAX, POSSIBLE?
Another question: is possible in some next version select use without Ajax or use ajax? I like me…

https://ww.wp.xz.cn/plugins/ajax-dropdowns/