1.) Please offer UI-color-schemes and support dark mode. The paper/backgound should be dark, the notes and texts bright. It is much easier to work late and long with dark display. This should not affect printing.
2.) Is it possible to shorten the extention of Dorico-Project-Files? Something like .dor would be fine 
Have you heard of flux?
It’s strange to use in the beginning but starts to feel very natural after some days. For me it released the eye strain without any dark mode needed. And it is system wide.
2.) .dork
@mikiworld: Not really what I want. I am used to work on dark surfaces and editors and it is much less distracting.
On MacOS you can instantly reverse the video anytime with Command-Option-Control-8. You may need to enable the keyboard shortcut in System Preferences.
1.) I actually suggested something similar but is related to the title bar color inconsistency with the theme. Your idea sounds good, and I was even thinking of making a feature request suggesting Dorico to allow users tweak the background color to lightgreen or lightyellow for the sake of users’ visual comfort.
2.) Maybe it is a trend since Visual Studio.net (probably 2002 or 2003) uses “.vbproj” or “.vcproj” as Microsoft’s first example of using long file extensions. This trend also copes with current practice which most macOS apps follow.