The WindowFrame, WindowPosition, WindowSize, and WindowName text tokens return information about the specified window. Each one takes a parameter indicating which window to use.
The parameter may be:
So for example, %WindowName%1% gives the name of the front window.
Like all coordinates in Keyboard Maestro, the WindowPosition and WindowFrame are from the top left corner of the main screen (the defined one with the menu bar on it, although this is less apparent now that the menu bar is on all monitors).