I've attached a screenshot. The button appears when you select the class definition tab in the browser. Press it and you get a dialog to enter a subclass name then the text <http://forum.world.st/file/t368903/subclassbutton.png> template for that subclass appears in the browser class definition tab.
This is from Pharo 9 on Linux (this is an older version 9 - not the very latest) -- Sent from: http://forum.world.st/Pharo-Smalltalk-Users-f1310670.html
