A rather clever puzzle, I think, with a title, in my case at least, that sat quietly & innocently by whilst holding the most obvious of pointers to the solution. Well done Madrigal!
I’ve just finished 2719.
In the terms of the 3 groups, I’ve got one group that uses the same two letter abbreviation, one where the words can each be prefixed with the same three letter word, but the other group of three I can’t see any connection. That’s assuming have the correct words of course.
Any hints?