You either have to assign his code to someone else or enter the new preparers code for each return.

If youre in CA, double check the CA info sheet, if memory serves the 3rd party designee name didnt automatically change even when I had changed the preparer code on the federal....this was years ago, maybe thats been fixed.

I tried changing his preparer code information to me but his information still rolled over to 2019 Organizer

Probably wont take until the return has been opened, so that wont help with batch printing organizers, sorry. 

The 2019 returns should all show your info though, without having to change the code on each return.