Private collaborative playlists

Currently, if you make a playlist collaborative it is necessarily public. This appears to make it so that *anyone* can add tracks if they chose to. I would prefer to be able to make a playlist collaborative, but only editable by people who I share it with directly (and preferably only visible to them as well).

I consider this not only a usability issue, but also a trust & safety issue, since someone could be targeted for harassment by having their collaborative playlists spammed.