I have a very similar use case to this post Auto select first available options from a variation on WooCommerce variable products and while the jQuery code provided almost works perfectly there is a shortcoming that if a user changes one of the dropdowns then all variations are cleared.
The OP of this post hasn't been active and i've tried a PHP solution but this doesn't work for multiple variations.
Has anybody had to implement something similar before and have any code they could share please?