INCOSE works with psychometricians to develop its exam content. These experts oversee the many volunteers who write, edit, and review exam questions.
Volunteers are all SEPs and are trained to write defensible exam questions. The current (early 2023) development efforts are focused on writing exam questions that are traceable to both the Fourth and Fifth Editions of the INCOSE SE Handbook.
Additional information about the knowledge exam is listed here: https://www.incose.org/systems-engineering-certification/taking-the-exam