My solution so far has been similar to the post suggested by @tkoolen, but more automatic (and complicated).
I upload code with rsync to the remote and run Pkg.develop(PackageSpec(D)) on all dependencies D each time the code is run. Not elegant, of course.
On the relative paths: what I tried was paths of the form “~/abc”; those did not work. I will try @tkf’s suggestion as well.
Thanks.