Condless

WooCommerce plugin that sets default attribute for variable products automatically if only 1 option is in-stock.
<a href="https://en.condless.com/default-attributes-for-woocommerce/" rel="nofollow ugc">Documentation</a> | <a href="https://en.condless.com/contact/" rel="nofollow ugc">Contact</a>
Variable product of T-shirt with color attribute (White/Blue/Black) and size attribute (S/M/XL): 
If only Black T-shirts are in-stock: default color (Black), default size (none). 
If only Small T-shirts are in-stock: default color (none), default size (Small). 
If only White and XL T-shirts are in-stock: default color (White), default size (XL).
<h4>How It Works</h4>
<ol>
<li>Before product variations is displayed to the customer, the plugin will check each attribute, and if there is only 1 in-stock option it will be set as the default.</li>
</ol>
<h4>Features</h4>
<ul>
<li>Stock: Set option as default when it’s the only 1 in-stock.</li>
<li>Per Attribute: Set specific option as default in all products with that attribute (from the Edit Attribute screen)</li>
<li>Top: Set as default the first option of each attribute.</li>
<li>Out of stock: Disable out of stock variations.</li>
<li>Add to Cart button: In archive pages display for variable products the attribute name instead of: “Select options”.</li>
<li>Select options: In single product pages remove the select options text if default attribute is set.</li>
</ul>

Default Attributes for WooCommerce

WooCommerce plugin that sets default attribute for variable products automatically if only 1 option is in-stock.

Kuuak

After setting up WooCommerce and defining product attributes, you can define the default attributes, as well as there order, to be automatically added to new product.
It will make the creation of new product more efficient and fast as you won’t need 
to add manually the attributes, and remembering the same order for each new product.
Tested with WooCommerce version 3.3.3
<h3>Contribute</h3>
Don’t hesitate to fork this plugin and submit pull requests in the <a href="https://github.com/Kuuak/woo-default-attributes" rel="nofollow ugc">github repo</a>.

Woo Default Attributes

Define default attributes to be automatically added in WooCommerce new product page.

Default Attributes for WooCommerce vs Woo Default Attributes