Top left corner piece accessible?

In the corner above the row selectors and next to the column headers, is there any way to put anything in there (text, image, etc.) and/or to make it active (clickable)? Also, is there a way to put a separator in there, since it looks like it is part of the first column header?

You can do all sorts of things with it, it's just another text area that you can work with. Anything that you can do with a DIV you can do there. To access it use setTopText(). You can pass in any valid HTML into the method to display text or images or buttons etc. Just use your imagination:

obj.setTopText("<button>Click Me</button>");