Documentation on custom draggable items

[ghost]

Hello,

I am trying to implement your formulize tool into my platform.
I downloaded the js and css files and am using jquery to formulize my div.
Everything works fine but I'm having some issues understanding how to build those drag and drop custom elements shown in the demo.

There is little documentation as to this feature and I'm a little lost.

So here is what I don't really understand. How do I create and define these custom elements? (I want them to be character strings . And how do I trigger their insertion on drop.

EDIT:
I managed to inspect your demo page and copy paste one of your drag and drop elements. I imagine I will need to handle the drag and drop aspect myself and use insert.

However when your elements are inserted they are of type "item" whereas mine are of type "unit". Is there a way to define custom data types? I am making a formula builder using string elements and I would like those strings to be somehow retrievable in the data.