How to delete all conversations all at once in iMessage? It's clear on how to delete conversations in iMessage one by one. Does anyone know how I can delete multiple or all conversations all at once? Thanks.
In Mojave the keyboard sequence is to first delete the message with Command + Delete And then keep Command pressed and press d 
You can't delete multiple message at once unfortunately, but keeping the button Command pressed and alternately press Delete and d makes the delete process a lot less cumbersome.