Hi Bucklash,
Thanks a lot for your answer which helps a lot.
I was not aware of chosen.js which a much better solution than the modal box I had in mind.
As I never used jQuery, I struggled a bit to find my path.
So here is what I've done.
1) I assume jQuery is loaded by default with Joomla ?
I've tested it using a "Script (JS)" field in my form, which gave positive result.
if (window.jQuery)
{
// jQuery is loaded
alert("Yeah!");
}
else
{
// jQuery is not loaded
alert("Doesn't Work");
}
2) "chosen.js" was not loaded by default.
I choose to load it using a custom module which I find to be cleaner than modify my RocketTheme theme.
The code I used to load "chosen.js" is the same found in Joomla Article Manager.
<script src="/media/jui/js/chosen.jquery.min.js?d5b4774e823e9d58911aca2f942a7b50"></script>
Had a hard time figuring out that JCE was wiping out my code when saving, but with the right parameters, it worked.
3) I've used a "Script (JS)" field in the HIDDEN section of my form to load this code when Document Ready.
$("#name_of_my_select_field").chosen();
4) Now I need to style the field as it is not at all like in Joomla (see picture).
But the work is done and I'm happy with it :D
Big THANKS to you, you made my day !