We'll if that is all you need, you could just add to the htmlToolbox.
If you looking at a html file, the toolbox window should show the HTMLToolbox.
If you now make some custom HTML, like;
<div class="form-group">
<label></label>
<input type="text" class="form-control" />
</div>
You can select it and then drag it into the toolbox.
Rename it. et voila.
I'm not sure on how to share this toolbox with others. But I suppose it is saved somewhere on disk.