Hi there @Caroline Nunes,
Welcome to the Community and thanks for posting your question regarding Salesforce Commerce Cloud and events.

I believe, it won't be possible to replace the current native integration events with newly adjusted variables that have been created.
Instead you will be required to send us custom metric using the Metric API. You will then have the ability to call the newly created variable in the API Call and update the flow's trigger to be paired to the newly created Metric and pull through that event information. I unfortunately can't advise on how to this aside from general guidelines as it's not a built-in integration with Klaviyo, however I can direct you to our partner page which will have mutual partners who have the ability to create and assist this for you.

In addition, I will reach out to different team members so that I can provide more information if available.

Thank you!

Alex