Simply add this CSS to Theme Options> Advanced Settings:
#nav-main ul.sf-menu, .nav-main ul.sf-menu {
display: none;
}
.mobile-nav-trigger-id , .id-kad-mobile-nav, .kad-header-style-three .kad-nav-three {
display: block;
height: auto;
}
If using the Simple Mobile Header option, use this CSS instead:
#kad-mobile-banner-sticky-wrapper {
display: block;
}
#kad-mobile-banner {
display: block; height: 60px;
}
#kad-banner-sticky-wrapper, #kad-banner {
display: none;
}