Change submenu animation (vertical left nav)

is there a way to change the fade in/out animation of the submenu? I’m using the “vertical nav left” and want the submenu to slide in from left. I’ve found out it’s been made by JavaScript (theme.js from line 524) but I don’t know how to override this JavaScript from the Parent Theme in the Child Theme.

Also I want the submenu to be the full height of the page. Any thoughts how to do this the best way?
Full Height solved: Have set my .sub-menu ul with a top and bottom padding auf 50vh, position: fixed and top: 0%.

Kind regards from Germany