I added some classes to your html for reference:
HTML
<div id="topNav" class="navbar navbar-default navbar-fixed-top">
<div id="bottom" class="container" style="margin-top:55px;border-left:solid 1px #f2f2f2;">
jQuery
$(function(){
$(".draggable-tag").draggable({
helper: "clone",
start: function( event, ui ) {
ui.helper.css('z-index','1050');
}
});
$("#topNav").droppable({
drop: function( event, ui ) {
$(this).find('.container .nav .tag-drag-drop').append(ui.draggable.clone());
$('#bottom').css('margin-top',parseInt($('#bottom').css('margin-top'))+40+'px');
}
});
});
Example: