How to delete PM

I do not see "delete option" in that box.
Somebody made this MUCH more complex and complicated than it used to be.

The "New Language" is "Leave Conversation". Which is not totally self-explaining.

LeaveConversation.gif

So there is anOTHER dialog box which asks questions oddly. "Accept future" might hide the conversation from your eyes, but keep it on the server, in case the same(?) conversation starts up again? And "Ignore" seems to close all future communication on this conversation. But what is a conversation? A Subject? One or more persons?

And why do we delete old private messages? Historically the forum operator set a limit, like "50". Is that still in effect despite 20 years of falling storage costs? Is there any way to see if I am hitting my PM quota now?
 
Coming back to this Delete PM's issue. "Leave Conversation" is what is offered but with that, if the corespondent happens to send another PM from his copy in his inbox then the whole conversation gets restored - which means it was never deleted , just hidden.

Something wrong with that idea. If you want to throw something in the trash , imagine the trash collector saying " OK, I'll just hang on to that. If I hear you're messing around with that sort of thing again, I'll bring the old trash back."
 
"Leave Conversation" is what is offered but with that, if the corespondent happens to send another PM from his copy in his inbox then the whole conversation gets restored -
I saw two choices, which seemed to amount to "hide for now" and "hide forever". I tried both on a recent conversation. The first option, the conversation started-up again the next day, as you say. The second, the conversation went silent (for me) and never started again. Maybe the other two persons stopped at the same time, but I thought it was like I quit forever.

....in fact I wrote this up already, with circles and arrows. There are two choices in an oversize dialog.
LeaveConversation.gif