Let me create new UI items

I often create layouts which I reuse, such as a Sharepoint page layout which contains a web page, tabs interface, list for the left side quick launch bar etc.
I export these to a Notepad file, and use the Import feature to import them to my Mockup. Would be great if I could store them inside the UI toolbar, perhaps in a "Custom" section where I could give them a name, and store the XML for creation of them