Custom Service Dialog Element Type

I need to create a customer dialog element information type under service catalogs. Is there any example custom code for this or documentation on how to accomplish this task? Ideally I want the ability to have two text boxes located horizontally to each other each that would get text input to them.

Also these text boxes would be assigned to their own variable like dialog_textbox1 & dialog_textbox2

Documentation for Service Dialogs can be found here:

At the moment the dialogs only support displaying the fields vertically.