Thank you Robin,
I created form-topic.php in my theme and added my taxonomies dropbox in the new/edit topic form.
The form is the original one
<form id=”new-post” name=”new-post” method=”post”>
…
Can you explain me in which file the system saves the data sent on submit?
And how to override or extend the save topic method to save also the values of the custom taxonomies?
Thank You!!!!