You had actually guessed right. The list of folders and paths used by the app are in:
~/Library/Application Support/Less app/lessDataFile.lessData
It's a binary plist (Property List) file, and from the look of the structure of the file, it's not meant to be messed with. It looks like an unintuitive serialization/dump of the internal state of the app.
It seems to store its preferences in this other binary plist file:
...but this file doesn't contain any of the folder paths used by the app. That's all in the
lessDataFile.lessData file you'd already found.
It's standard practice for Mac OS X apps to store their preferences in a plist like that (that location, that naming scheme).
You can read and edit binary plist files with Xcode (and many other programming-oriented text editors for Mac OS X), or with the command-line tools
defaults(1). Or you can convert them to XML text files with
plutil(1). Some tools for working with plists expect the file name to end in
.plist, so keep that in mind if you're struggling to get a tool to open the