@krzyzanowskim The oldest reference I found is this Pastebin from 2019: https://pastebin.com/bm3qiizz

It contains references to other flags, e.g.:

· NSLogUnusualAppConfig (documented at https://mjtsai.com/blog/2013/12/31/defaults-for-debugging/)
· NSConcurrentViewClasses and NSDebugConcurrentViewDrawing (probably documented in some AppKit release notes, https://spec-zone.ru/RU/OSX/releasenotes/AppKit/RN-AppKitOlderNotes/index.html)
· NSMightNeedToWorkAroundBadAdobeReleaseBug (https://twitter.com/chrisatlatenite/status/1214832204687134720)
· NSVisualEffectViewDefenestratorModeEnabled (?)
· most of https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/EventOverview/TextDefaultsBindings/TextDefaultsBindings.html#//apple_ref/doc/uid/20000468-610084