When you create a third party trigger for Klaviyo, the Made with Intent client script will invoke the Klaviyo custom trigger code.
How to trigger Klaviyo forms in campaign manager
Create a form in Klaviyo
Under targeting and behaviour, choose only show on custom trigger
βEvery Klaviyo form has an ID, e.g. KLVpXn. Copy and paste this ID into the Made with Intent campaign modal.
Publish your form in Klaviyo - it won't fire until the custom trigger code is executed
Publish your Made with Intent campaign. When the experience segment matches, the Klaviyo custom trigger code is run.