Is there a way to dynamically add grouping in multi select using this formation

<!-- language: lang-js -->
var data = [
    {label: "ACNP", value: "ACNP"},
    {label: "test", value: "test"}
];
$("#multiselect").multiselect("dataprovider", data);

Yes, you can now add groups with dataprovider thanks to this pull request

See the documentation on .multiselect('dataprovider', data).

Demo in jsFiddle

You can compose like this:

<!-- language: lang-js -->
var data = [{
    title: 'First group',
    children: [{ label: 'Cheese', value: 'cheese' }, 
               { label: 'Tomatoes', value: 'tomatoes' }]
    }, {
    title: 'Second group',
    children: [{ label: 'Mozzarella', value: 'mozzarella' }, 
               { label: 'Mushrooms', value: 'mushrooms' }]
}];

$('.multiselect').multiselect('dataprovider', data);
<!-- language: lang-html -->
<select class="multiselect" multiple="multiple"></select>