I'm not sure this is a good idea. And I think there is no proper way to do that.

The first question that springs to mind is: Why?
The console is just for debugging, error reporting etc.  It doesn't appear in an applet or exported application and you wouldn't want to use it for anything else as it needlessly uses resources...

TBH I don't know how; but that's because I've never had a need or desire to do it.

EditorConsole.java does have a clear method but i don't think PApplet have access to that class... so i think what you're asking is impossible but maybe im wrong...

i once wanted to clear the console, so i just printed some empty lines. maybe thats already what you need.