Hello,
There is no setting for this yet, but we will add one in the next release of HikaShop: you will be able to mark a product as selected by default when it is used as an option, directly on the product edit page.
In the meantime, you can do it with a small override of the "option" view. Go to Display > Views, open the product "option" view and save it once so HikaShop creates the override (your change is then kept on updates).
In that file, find the line that builds the option selector, it passes (int)$value as the selected value and looks like this (the helper may read JHtml or HTMLHelper depending on your version):
$html = JHtml::_('select.'.$select.'list', $option_values, $map, $attribs, 'value', 'text', (int)$value, $id);
Just above that line, add:
if(empty($optionElement->variants) && $optionElement->product_id == 123)
$value = $optionElement->product_id;
Replace 123 with the id of your "Support" option product. That option will then be pre-selected on the product page, and the customer can still unselect it. To pre-select every option that has no variants, remove the "&& $optionElement->product_id == 123" part.