Snippets: Change Mobile Menu Dropdown Arrows to Plus Icon

/* Show plus icon by default */
body .wpex-open-submenu {
    content: "\002B" !important;
    font-family: "Arial";
    font-size: 16px;
}

/* Show minus icon when active */
body .wpex-open-submenu[aria-expanded="true"]{ {
    content: "\2212" !important;
}

Result:

All CSS snippets should be added via a child theme's style.css file or using the built-in Custom CSS panel.