Warning! This is a very powerful extension, and is for the more technical users.
This plugin enables the use of subforms within any extension that supports Joomla custom fields. Currently, this includes users, contacts, and content. It will be impossible for me to fully describe the possibilities of this plugin - but I hope my video demos and documentation will help. I will give a brief description, and then list features.
The subform field type is very powerful and now that the capability is delivered to custom fields, you can collect groups of data and even repeating data (this plugin supports repeating subforms). Defining your own XML form, you can customize the collected data to meet your needs. Create as many or few fields as you need for your subform. This plugin also implements translation for field labels and descriptions. It doesn't stop there, the output can be customized as well, with a PHP output template. Implemented on this page is a "Twitter Card" subform, which outputs meta tags in the document <head>.