Hello @KaraL87689 ,
At this time, there is an issue with CPE emails created from within a legacy automation series not having their headers available to edit. The only workaround would be to make the email wholly outside the automation series, or at least just getting it started, and then copying that into the series. You can copy the step from within going forward after that, and it should retain the ability to have its own individually set subject line.
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