Hi @Laurent,
Thank you for sharing with the Community.
We do not have any natively built integrations with the Wishlist King app in Shopify, so this wouldn't be possible out of the box. However your developers may be able to set up a custom metric via the API. They can review the API documentation here. The apps also may offer a way to integrate with Klaviyo via API directly. Wishlist King by Appmate specifically advertises that they do integrate with Klaviyo but I could not find specific documentation about the process.
If you still wish to pass events from this app into Klaviyo, you can still certainly do so by taking advantage of Klaviyo's API. This would be a custom integration you built to be passing your desired events into Klaviyo. If you are familiar with a developer or have the skills to do so, I would recommend referencing the following articles if you wish to pursue this:
Getting Started with Klaviyo APIs
Track and Identify API Reference
Klaviyo's REST API References
Since this would be a custom integration, Klaviyo would not be able to assist in its creation or troubleshoot the usage of this connection as it would be outside our scope of support.
The only alternative would be to manually track these customers and profiles then send them a campaign through Klaviyo.
All the best,
Alex