Я предполагаю, что нет встроенной поддержки для остающегося нажатого элемента, поэтому я снова визуализирую элемент select вручную, что-то вроде этого:
$('#multiselect').multiselect();
var arr = [];
$('#multiselect option').each(function() {
// console.log($(this).text() + ' ' + $(this).val());
arr.push($(this).text());
});
$('button').click(function() {
$("#multiselect").empty();
for (var i = 0; i < arr.length; i++) {
var node = document.createElement("option");
var textnode = document.createTextNode(arr[i]);
node.appendChild(textnode);
document.getElementById("multiselect").appendChild(node);
}
});
<script src="https://code.jquery.com/jquery-1.11.2.min.js"></script>
<script src="https://netdna.bootstrapcdn.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
<script src="https://www.jqueryscript.net/demo/Two-side-Multi-Select-Plugin-with-jQuery-multiselect-js/js/multiselect.js"></script>
<link href="https://netdna.bootstrapcdn.com/bootstrap/3.3.4/css/bootstrap.min.css" rel="stylesheet" />
<div class="row">
<div class="col-xs-5">
<select name="from[]" id="multiselect" class="form-control" size="8" multiple="multiple">
<option value="1">C++</option>
<option value="2">C#</option>
<option value="3">Haskell</option>
<option value="4">Java</option>
<option value="5">JavaScript</option>
<option value="6">Lisp</option>
<option value="7">Lua</option>
<option value="8">MATLAB</option>
<option value="9">NewLISP</option>
<option value="10">PHP</option>
<option value="11">Perl</option>
<option value="12">SQL</option>
<option value="13">Unix shell</option>
</select>
</div>
<div class="col-xs-2">
<button type="button" id="multiselect_rightAll" class="btn btn-block">
<i class="glyphicon glyphicon-forward"></i>
</button>
<button type="button" id="multiselect_rightSelected" class="btn btn-block">
<i class="glyphicon glyphicon-chevron-right"></i>
</button>
<button type="button" id="multiselect_leftSelected" class="btn btn-block">
<i class="glyphicon glyphicon-chevron-left"></i>
</button>
<button type="button" id="multiselect_leftAll" class="btn btn-block">
<i class="glyphicon glyphicon-backward"></i>
</button>
</div>
<div class="col-xs-5">
<select name="to[]" id="multiselect_to" class="form-control" size="8" multiple="multiple"></select>
</div>
</div>