It’s hard to get this to work reliably for the reason that when you press the hot key once, the only way Keyboard Maestro can know to wait for a second tap of the same hot key before deciding which macro to fire, is to put in some kind of pause so Keyboard Maestro can think about it.
I find a simpler and more reliable way to get two alternative results from the same key is to add in an extra modifier -
⌘D fires one Macro
⇧⌘D fires a different but related Macro
This is also common behaviour for many inbuilt App shortcuts so I find it easy to remember too.
For the problems inherent in the double-tap approach a search found this: