Script Debugger has a collection of preferences settings which are not alterable via Script Debugger’s Preferences panel. This post documents all of Script Debugger 6’s hidden preferences.
One I noticed seems to have incorrect documentation. It says:
PrefMaxRecentDocuments
Type: integer, Default: 15
If set, …
The default appears (at least on my mac) to be unset (i.e., the domain/default pair does not exist), and not 15. If unset, then the number is whatever is set in System Prefs > General (of course, that may be 15 on your machine; it’s 50 on mine).
If the pref is set, then the number is presumably whatever integer the user sets it to.