Simply hold alt and drag any midi part while hovering over the very top menu. The black stop sign will change to a tiny plus arrow and when you let go of the mouse, a pop up dialogue appears asking where to set the project folder. Thought i would share. Thanks
That’s not for the existing project. It’s for a new project, will subsequently be created.
My mistake. I should of tried it before posting 
It’s still a bit of an Easter egg. I never knew that was possible- and maybe it’s not supposed to be! 