This sounds similar to the question linked to below. There wasn't an obvious solution as there is no condition that allows a trigger based on mouse location.
It is fairly simple to have the Palette triggered with a right-click of the mouse in a specific App when that App has a specific Window Title. But that would be a right-click anywhere on screen, not just in the Window Title Area. You could achieve that like this:
EDIT - Actually there might be a way to make a condition based on mouse location by saving the current mouse location to a Variable and then comparing that to an ideal location (near the top of the window). If the current location is within a range of the ideal location (the window title bar) maybe that can be used as an additional condition in the example above. But it seems like a lot of work to invoke a Palette...
Why not just give all your Application Group Palettes the same hot-key? Pressing this hot-key will open the specific Keyboard Maestro Palette for whichever App you are in. That's what I do. In my case I use ⌥⌘K as the same hot-key for all my Groups.
