List in params with Nested Dynamic form

Thanks for your reply!

If by nested form, you mean a tag inside another, no.
What I mean is a nested list of checkboxes, re-used everytime the client clicks “new target”. So a html.eex page inside another one, basically. And I want each of those html to return me a target_param(list of check_boxes checked for each target) that will be used to save the result in my database