Well, we will write a little code first. If you are not scared by that fact, go and install AutoIt. It is a great scripting language for Windows. It saves the day when you just want what you want to be accomplished and not worry about anything else. Anything that comes up to your mind, first check this thing, if you cannot find it, or it is limited in some sense, only then try implementing it wholly by yourself. Fortunately, what we are going to do is actually quite basic, so it has all that we need.
Here is my code for hiding and showing the ToDo gadget based on a hotkey.
Ozan Safi 