After taking a cursory glance at the sources, It's rather unique in a way that it's GTK based yet looks nothing the average GTK application. I wonder what made them pick GTK instead of QML or even something unique like many DAWs do.

btw congrats to the team, I'm not musically gifted to give an opinion on how usable it is, but the design looks very crisp and more akin to something you see in closed source apps with an army of designers behind them.