From your documentation adding an editable="true" attribute to the select, can easily extend the options list. I've done that, but it does not work. From your site, it works, but from the snippet site, it does not work.

I'll need your assistance to get it working on my site, thanks.

The snippet url: Add new option to select

Sample Code:

<select class="mdb-select md-form" editable="true" searchable="Search and add here...">
 <option value="" disabled selected>Choose your option</option>
 <option value="1">Option 1</option>
 <option value="2">Option 2</option>
 <option value="3">Option 3</option>
</select>
<label class="mdb-main-label">Example label</label>