Modify serialized data

Hi!
I’ve been experimenting with this fantastic plugin; it’s very powerful.
But I haven’t been able to figure out how to modify serialized data.

I need to correct several variable product download URLs in WooCommerce.
I managed to correctly configure the advanced search filters and view only the URLs I need to modify. But when using a regex, each URL changes the number of characters, and I don’t know how to modify both, the URL and the number of characters (s:#) at the same time.
Is this possible? How?
Thanks for your amazing work!