Hey BTW, why Units? Why not just Put it in Pixels for default instead units? We are working with digital 2D images for draws and animations dont editing documents for magazines or impress, think in the Random people or new users, all the animation2d and Painting programs have they metric system units in Pixels by default, with Synfig you must need to be like an atronaut to go the menu edit, preferences, system(i think, forget ), metric unit. . You want more people use the program think in that people the new users dont know nothing about the program, make easy and more friendly for they. I love Linux, but Im a Digital Artist not an informatic programer guy, for that reason I return to Windows because I lost more time try to configuring and try make the softwares work well than making my draws.
Ah other one: why time line Start for frame 0? It must start from frame 1, frame 0 dont exist, frame 0 is when you have no draw (in the moment that you do a simple doodle, point or line it be the frame 1.), I think it must start from frame 1 for default (but Synfig time line is more like a 3D program, but look even blender start the timeline in frame 1) and if some hipster want that they project start from frame 0, then that he have need to go the preferences and change it, but not make to the new users do all that changes