Discovered this by accident while trying to sort out keyboard mappings and such on Win.
You can display the keyboard layout for Helena by using the Windows -> Characters menu item. And then click the icon to make it a floating palette. Now there are three checkboxes on it for letters, diacriticals and special characters. If you uncheck one (assuming all checked to begin with) the palette shrinks a little. You then check the box again and the window increases in size. But in doing each check and uncheck the palette moves down the screen a little and slightly to the right.
Not especially serious but peculiar and I'm sure its not intended.