A few years ago a group of people (Glimpse NX) tried to reimagine GIMP's user interface with GTK3 technology like headerbars, but they didn't have a great solution for accessing all the features that are in GIMP's main menu. Turns out, there is a possible solution available in a new 3D CAD program called Dune 3D, as well as in an older program called Horizon EDA by the same developer.