How can I change the Working Directory of Pluto?

I know how to do this with Jupyter, but there is scant info on the Pluto config file or where it is. My C drive is too full and I don’t like cluttering up my home directory, so I use an external drive.

I’m not entirely sure if/how this is done for a new, unsaved notebook, but saving a notebook as a .jl file somewhere seems to change the pwd appropriately.