CTRL+H is widely recognized key combination for search and replace action. I would not expect to ever meet an editor that doesn't support it - further more that it will be an editor for programmers which suffers such flaw.

I assume CTRL+H was simply omitted because pressing CTRL+F also allows you to replace in text. But this combination is something everything is used to and should be assigned to both not annoy people and to reserve this combination as taken. Because you would be foolish to assign other function to CTRL+H.