So I was looking for an form-UI solution that, after an user filled it with data, it would automatically create a JSON and it seems that JSONForms is what I needed.
The only thing is that my JSON is not fixed.
Is it a thing that JSONFroms thake into consideration, to generate on-demand the JSON (mainly add specific repeated array item) and then, when the user is ok with that, generate the form for the user to fill it with the actual data