I looked everywhere and saw no mention of it. The closest workaround I've found so far is to run a script whenever I open Arbortext Editor: window_set(current_window(), "canvasbackground", "gray5")
This only partially helps though (screenshot attached). Ideally, on a Windows 10 machine, Arbortext (and everything else, for that matter) should check the system-wide setting for light/dark mode and automatically apply the appropriate mode without user input.
Dark mode would work like most other modern applications with white or bright text on a black or dark gray background. If that's not feasible, please at least add an option to Tools-->Preferences... to manually toggle Dark Mode on/off. Preferably on/off/automatic with default to automatic though.
The bright white background causes eye strain (especially when most almost every other open app is in Dark Mode). Lastly, consider the electricity consumption saved from all the screens of all the users for a long time.