The title is my question. I googled and try something like
mysql> !\\ clear
mysql> !\\ cls
mysql> system cls
mysql> system clear
blah blah ...
Open Properties by clicking the upper left console window icon, go to Layout tab, take note of the value set in Screen Buffer Size->Height
, and change it to 1. Click OK.
You'll see a 1 row console. Open Properties again and change that value back to what it had before. Resize the console down and you'll have a clean console.