After more inspection, I have found that it is designed with CSS. Please use this CSS to Template Options -> Custom Code -> Custom CSS
body.ltr .sp-megamenu-parent .sp-dropdown.sp-dropdown-main.sp-menu-full>.sp-dropdown-inner:before {
content: "";
position: absolute;
top: 0;
right: 58%;
bottom: 0;
width: 3000px;
background-color: #fff;
background-image: linear-gradient(95.55deg, rgba(255, 22, 111, 0.5) 4.25%, rgba(255, 109, 47, 0.1) 93.67%);
}
body.ltr .sp-megamenu-parent .sp-dropdown.sp-dropdown-main.sp-menu-full>.sp-dropdown-inner:after {
content: "";
position: absolute;
top: 0;
left: 100%;
bottom: 0;
width: 3000px;
background-color: #fff;
}
and you will also get similar thing. But this is not all. There are more styling used in Wimble template. Unfortunately, we do not provide customization support. So, I cannot make this for you. You can hire someone to do the CSS trick for you.