Magento – Magento 2 : New Configurable product – selecting existing simple products manually

I got the solution to the above requirment..

$product= Mage::getModel('catalog/product')->load($configId);
    #Check if the product has children
    if ($product->type_id == 'configurable') {
        $options = array();
        // Get any super_attribute settings we need
        $productAttributesOptions = $product->getTypeInstance(true)->getConfigurableOptions($product);
        foreach ($productAttributesOptions as $productAttributeOption) {
                    $options[$product->getId()] = array();
                foreach ($productAttributeOption as $optionValues) {
                    $val = $this->trimValue($optionValues['option_title']);
                    $options[$product->getId()][] = array (
                        $optionValues['sku'] =>  $optionValues['attribute_code']."=".$val           
                    ) ;
            }
        }

Technically configurable products ARE simple products.

In Magento a configurable product is comprised of simple products which have permutations of values that make the parent unique. These attribute values, called super configurable attributes, are the values that make each SKU unique.

Example

Let's take an example of a t-shirt. Our t-shirt can have two super configurable attributes, size and color. For simplicity let's say we only offer two variants of each of those attributes:

• Red Small T-shirt
• Green Small T-shirt
• Red Large T-shirt
• Green Large T-shirt

Easy enough.

For a configurable product to be... well... configured; you would have to have created each of those simple SKUs. That means that you likely have those simple SKUs already.

So, no conversion is needed. Simply make sure that each of those simples are now Visible and In Stock and not Disabled. Then assign them to a category and you should be in business!