the easiest is to add items to the popup (only in a subclass of the EditingTool)

off course you can always use NSMenu and pop up a menu in a view at specific location

from mojo.events import EditingTool, installTool

class TestTool(EditingTool):
    
    def additionContectualMenuItems(self):
        
        return [("Test item", self.callback), ("submenu", [("Test Item", self.callback), ("Test Item 2", self.callback)])]
        
    def callback(self):
        print "hello world"
        
installTool(TestTool())