The color was not changed in the app itself, the Active title bar color comes from the Windows 10 interface.
Here are my exact settings. (Notice "Dark Mode" is also switched on.)
I am trying to reduce glare and eyestrain when I can in Windows 10, so my Inactive title bar was changed to a dark color with WinAeroTweaker 0.12.1.0 under Appearance in that program. (I wanted a darker, less harsh alternative to the bright default inactive title bar color.)
I appreciate your work on compatibility with LibreOffice Writer.
Ctrl-N for a new document in LibreOffice should pop it open in a tab, as tabbed programs like Firefox, Chrome, Visual Studio Code, Notepad++, etc. do.
My 30-days of beta-testing Groupy are near an end, as the program notified me, so I have uninstalled it, since Groupy is not quite ready yet. I am still willing to take the time to provide feedback on here about my experiences.
If Groupy irons out its issues I will certainly be purchasing it. The software has great potential.