The javascript API allows you to interact with the menu via custom javascript.
The Functions API allows you to perform actions on the menu.
The Events API allows you to trigger actions when menu events occur.
You can place custom Javascript in a child theme, custom plugin, or code snippet plugin – it’s up to you.
Please note that, depending on the order in which you enqueue your scripts, you may need to disable UberMenu’s Remove JS Conflicts setting in the UberMenu Control Panel > General > Script Configuration