I just purchased and installed Groupy (version 1.32). I couldn't get it to work at all: moving a window's title bar on top of another window's title bar got a resounding yawn from Windows 10 Pro (version 1909). I tried a cold reboot - no dice.
Are there any limitations as to kind of windows (I also use CMD.EXE's DOS style windows)? Do window widths have to match?
Here's me trying to latch a Google Chrome window on top of a Firefox window:
