Well, I have ~/Projects for all my projects, Nim or else. There I clone all my repositories and I'd like to avoid having a nested directory structure if possible, and avoid cluttering ~/Projects with Nim stuff.
So I have ~/Projects/app cloned, and if I can optionally tell it to use ~/Projects/lib that would be perfect, but else I'd prefer having the dependencies I don't touch out of the way inside ~/.Nim or elsewhere.