Add sub-menu indicator wordpress with wisteria

Hello I want to put a mark-indicator on the main top menu where menu items that have sub-menus show an indicator and if a menu item does not have sub-menus simply do anything.

I saw some sites that have mini arrows indicating what menu items have sub-menus.

I heard with jquery is possible do easy but I don’t want to use jquery and I think is better maybe entering something in CSS, functions.php. I’m using the wisteria theme:

https://www.ads-software.com/themes/wisteria/

Any ideas? or code to insert?