in the age of 500MB apps (thanks to electron); it is refreshing to see a sub-50MB app again.
Reaper and Pro Tools (and many other DAWs), in contrast, had the source material in one folder and the session file essentially just documented the edits. These small session files could be exported even via email.
The .aup3 format was one of the reasons why I decided to ditch Audacity3 for radio editing back in the day. And, it used to lag heavily when I had a project with several hundred cuts done via "ripple editing". All this was years ago, though.
I concluded that Audacity v1.2.6 was the high point of this software and, indeed, tried to go back into using that one for a while (in 2019 or 2021 or so)! It was fast enough, very simple, young, raw, robust, but it still had its early 2000s open source enthusiasm charm. :)
As a blast from the past, here's a 2002 publication by the original authors of Audacity on the original file format: https://www.cs.cmu.edu/~rbd/papers/RBD-papers%20renamed/A%20...