I am using the publish_{cpt} action when creating posts on the backend to set meta field data based on the fields, and I want to fire these actions when posting in the frontend too.
I tried using add_action('rwmb_frontend_after_save_post', 'custom_function'); but that didn't work.
Can you please share the code that you are using to set the field value? You can use the helper function rwmb_set_meta() or WordPress function update_post_meta() to set the field value.