Hiding Menu Items on Mobile Menu

In my main Nav Menu, I have a single menu item that triggers a modal window with a form.
That’s great. Works fine.
However, on the mobile overlay menu I would like to hide that single menu items, so I can replace it with one that goes to a page.
Normally, I would just a unique class to the menu item, and hide it using the display property within a media query.
But I’m not able to do that because the mobile overlay menu in Enfold appears to drop the classes that are added in the Menu settings.

So, I guess I’m wondering if anyone has any suggestions for ways to hide single menu items when using the overlay mobile menu.

Thanks.