Hi Jay,
Thanks for writing.
Your requirement I call it "composite control". Beside Address field, another good example is Name field which can have First Name and Last Name.
Please refer to sample source code of Single Line Text at
https://github.com/limcheekin/jquery-form-builder-plugin/blob/master/src/js/jquery.formbuilder.singlelinetext.js. Composite control is not so much different from simple control like Single Line Text except it is more complex.
First, you would need to put all fields to _html option of the control js file, eg:
_html : '<div> \
<div><label><em></em><span></span></label> \
<input type="text" class="firstName" /> \
<p class="formHint"></p></div> \
<div><label><em></em><span></span></label> \
<input type="text" class="lastName" /> \
<p class="formHint"></p></div> \
</div>',
You need to layout fields of the composite control appropriately using CSS.
Then, add settings specific to the composite control.
Lastly, implement the server side functionality of the composite control.
Hope the idea above help.
Best regards,
Chee Kin