apres une pause cafe (pour les neurones)
j'ai modifie comme suite:
{form_field form=$form field='product_sale_elements_id'}
{loop name="order_pse_quantity" type="product_sale_elements" product="{$ID}" order="quantity_reverse" limit="1"}
<input id="pse-id" type="hidden" name="{$name}" value="{$ID}" {$attr} >
{/loop}
{/form_field}
{if $pse_count > 1}
{* We have more than 1 combination: custom form *}
<fieldset id="pse-options" class="product-options">
{loop name="attributes" type="attribute" product="$product_id" order="manual"}
<div class="option option-option">
<label for="option-{$ID}" class="option-heading">{$TITLE}</label>
<div class="option-content">
<select id="option-{$ID}" name="option-{$ID}" class="form-control pse-option" data-attribute="{$ID}"></select>
</div>
</div>
{/loop}
<div class="option option-fallback">
<label for="option-fallback" class="option-heading">{intl l="Options"}</label>
<div class="option-content">
<select id="option-fallback" name="option-fallback" class="form-control pse-option pse-fallback" data-attribute="0"></select>
</div>
</div>
</fieldset>
{/if}
j'ai rajoute au debut cette boucle
{loop name="order_pse_quantity" type="product_sale_elements" product="{$ID}" order="quantity_reverse" limit="1"}
....
comme le javascript par defaut affiche le produit indique dans le input id="pse-id"