Executive producer, Kurtzman's old job.
Huh? The first season had 9 different people credited as executive producers at various times, ranging from creators and showrunners to the director of the pilot to a couple of people who are basically just financial partners. "Executive producer" is a title that covers a multitude of different roles in a production, from creative to logistical to business.
Kurtzman's role on season 1 was basically the equivalent of Greg Berlanti's role on the Arrowverse shows or
Riverdale, or Joss Whedon's role on
Agents of SHIELD -- he and his partner Heather Kadin (also an executive producer, but on the logistics/business side rather than the writing side) are the heads of the production company that makes this and various other shows. In Trek terms, Kurtzman and Kadin were basically in the Herb Solow/Rick Berman role, the people who hire and oversee the showrunners. When showrunners Berg & Harberts were let go, Kurtzman essentially stepped into what had been his subordinates' role to fill the gap -- much like when Berlanti moved back into a more hands-on showrunner role on
Supergirl and
The Flash once Andrew Kreisberg was dismissed. It sounds like Duff will be his co-showrunner, perhaps, or something close to it.
Note that Olatunde Osunsanmi is also getting upped to executive producer, but in a totally different role. It sounds like he's in the "producing director" role that's becoming increasingly common, a director who stays on with a show permanently and oversees the logistics of its shooting, and coordinates with individual episode directors to maintain a consistent tone.