Hi @birous,
If you are wanting to change the data before the form is submitted, you’ll need to this via JavaScript.
You should be OK to just hook onto the submit event and modify the form values as needed using jQuery – all form fields have attributes that will allow you to find what you need.
Alternatively, you could write your own JS submission step using the internal (undocumented) system. If you take a look at how we are hooking AJAX handling in the repo, you can see it’s a pretty basic system to use. Just note that you’ll want to use an early priority so you modify the data well before other JS handlers try to use it.
Cheers,
Phil
