Wisteria

Go to Appearance > Customize > Additional CSS and paste in the following:

.mega-menu-primary .main-navigation {
    display: block;
}
.mega-menu-primary .toggle-menu-wrapper {
    display: none;
}

.mega-menu-primary .main-navigation {

display: block;

}

.mega-menu-primary .toggle-menu-wrapper {

display: none;

}

Max Mega Menu Documentation