Good, this is perhaps a bit confusing. I am trying to adapt a mod to make it compatible with the DATA file of an existing one.

So what I need is to generate the DATA with the same structure as the other mod. At the moment after making some small modifications I have managed to leave it as the image on the left, but I need it to have the same structure as the image on the right.

That is to say: that the name of the item "Box" is directly the general title of the item. As shown in the image on the right. In the same way with the names of the elements, I don't want the field to be called Item. I want the field itself to have its name.

Would anyone know how to tell me the theory of programming differences?
Address perhaps between Diccinaries and Lists?

Take a look at the Economics plugin. I believe I have an example in it. Basically just read the existing, reformat how you'd like, and save.

You can "convert" data files using different json attributes if you are using a class for your configuration/data file. You can open, for example, Skins to see how it converts old skins list to new one.