/* Show plus icon by default */
body .sidr-class-dropdown-toggle:before {
content: "\002B";
font-family: "Arial";
font-size: 16px;
}
/* Show minus icon when active */
body .sidr-class-dropdown-menu li.active > a > .sidr-class-dropdown-toggle:before {
content: "\2212";
}
Snippets: Change Sidebar Mobile Menu Dropdown Arrows to Plus Icon
Result:
