Want to share a house with my other computer but not with the public gallery

you could also save the folder on some cloud thing or send the file to yourself via email or something probably works too
(say you could just have save file that has build placed in it and send that to yourself)

usb is really the easiest though it doesn't take much space on the usb and you can use usb that has other stuff on it
also obviously you can delete the file from usb once you are done

I also doubt your partner would have problem lending you usb for just one little thing,
that is unless they are government agent and the things on that usb are top secret information
in which case i would be worried your partner is entangled in alien conspiracy