Digging into forms, I have come to understand (or just experience) that customizable components’data like Checkbox Group are not included in form value, as I described here: How can I customize form fields design with out disabling simplified? - #4 by jay-dee
So far I have found no way to turn the value of a form field checkbox, which is boolean, true or false, into a text data that could be included in form value. Form value does not seem to be modifiable or accessible from form fields interactions.