FYI, this is backward compatible to at least macOS 10.5 from 2007 so I didn't wrap the function with a version check.  GNUstep has had support for at least six years (the Emacs documentation says GNUstep is still "alpha" anyway, right?).

On Thu, Apr 3, 2025 at 12:46 PM Ship Mints <shipmints@gmail.com> wrote:
This function allows one to visually differentiate multiple running Emacs sessions by icon in the doc or application switcher using the icon badge.  For example set the badge to the Emacs version, or add "test" to indicate an instance launched for testing.  It can also be used to indicate pending items for MUAs or whatever someone wants.  This very simple feature has been on my list for a while...

-Stephane