Notepad was (before I decided to go ahead and purchase Groupy and closed Notepad) grouped with 2 instances of Scrivener, 1 of Zotero, and 1 Google Chrome.
I put the laptop to sleep using the keyboard last night rather than shutting the lid, and when I woke it up this morning everything was ungrouped, but that may be because everything (!!!) (other than Zotero) was no longer running.
I'll try this again tonight and see if that happens again. And, yes, I'm sure I chose Sleep, not Shut down or Restart.