The latest [revised] checklists on electrical fire/smoke of unknown origin are still based on the philosophical premise that the origin can be traced by following a logical chain of "isolating" and "load shedding" of circuits and busses. The dangerous presumption of this approach is that somehow the fire/smoke can be identified and stopped before total electrical shutdown [all generators turned OFF] becomes necessary.
As demonstrated by the SR111 calamity, the Air Canada DC-9 at Cinncinati, . . . The first trace of smoke in all cases must be treated as an extreme emergency, as an imminent catastrophic event.
In the case of electrics, the new checklists should be taylored to that presumption: All electrical power OFF as an immediate action item. Troubleshoot electrical smoke/fire of unknown origin in reverse order of today's checklist logic.