Hey there, @nik98! Thanks for contacting us. I’m happy to help you.
As I understand, currently when a variation is not available it does not show on the product page, correct? This is the default on WooCommerce, if you have checked the option to hide out-of-stock items.
But what you want to happen is to show the variation greyed out and unselectable, right?
Please note that to do that you would need to use either a third-party plugin or custom code.
You can search on the Plugins > Add New section of your dashboard or on a search engine like Google, for example.
Please note that we do not provide support for third-party plugins, so it is good to check the plugin thoroughly to see if it is reliable. You can find more about this in this guide.
If you rather use custom code, while we also can’t provide support for code customization as per our support policy, we do our best to offer advice and direct you to appropriate resources.
You can visit the WooCommerce Facebook group or the #developers
channel of the WooCommerce Community Slack. We’re lucky to have a great community of open-source developers for WooCommerce, and many of our developers hang out there too.
Please let us know if there’s anything else we can do to help or if you have any questions.
Have a wonderful day!