The traditional expression used by someone trying to abbreviate a lengthy, complicated tale was “to make a long story short.”
This has now been abbreviated to “long story short.” One rarely hears the original form these days.
Now I hear people saying “long story” and following it with the short form of the story. This strikes me as a little too short, too much like the traditional “it’s a long story,” which was followed by the long form of the story.
“Long story” for these people seems to mean the same thing as “in short.”