Suppose you want to make Burger appears on Desktop, next to Navigation, like this:

You can use this code to the Custom CSS box

div.header-burger {
    display: -webkit-box !important;
    display: -ms-flexbox !important;
    display: flex !important;
}

If you have a header button, the burger will appear next to the button, to move it next to navigation, use this new code to the Custom CSS box

div.header-burger {
    display: -webkit-box !important;
    display: -ms-flexbox !important;
    display: flex !important;
}

div.header-burger {
    order: 2 !important;
    margin-left: 1.5vw;
}

div.header-actions {
    order: 3;
}