@B.Wilson Yes and no. I suppose ⎕SE.⎕WX doesn't default to 3 (maybe it should?), so you either have to set ⎕SE.⎕WX←3, or use ⎕SE.(⎕WS'Event'('SessionPrint' 'P'))

@B.Wilson Also, I think this assignment syntax (not using ⎕WS) really should use onSessionPrint not just SessionPrint. I'm confused as to why it works by me!

@Adám Ah. Looks like 3=⎕SE.⎕WX by default for me, but explicitly using ⎕WS did the trick.

Could you try it with onSessionPrint←'P'?

@Adám Success.

Didn't realize that "really should" meant it was working like that Right Now!

Ah, okay, and just set ⎕SE.onSessionPrint←0 to restore printing.

Yes.