Modify "Add to document builder" pop-up with Page Composer

We have a use case where we need to modify the "Add to document builder" pop-up, in "Process Requisitions" page.

The change is related to the need to perform some custom validations on selected requisition lines before the purchase order is created, so the idea is to substitute the "Ok" button in the pop-up with a link to custom report execution and process requisition REST API in case the validation is passed.

But it seems that pop-up is not accessible for page composer edit.

Can someone tell if (and how) the above change is possible with Page Composer?

Thanks