Share some things with friends only (Public - Shared with Friends - Private)
It would be great to be able to give people the ability to view some lists (e.g. the watchlist) that are not public for anyone.
There are several ways which come to mind:
This could be a third option next to public / private: "Share with ...".
It could be possible e.g. for all those who I am following and who follow me vice versa, or ideally a specific group I can define individually.
It could also be an option to share all private groups with specific people (or the followers I am following, see above).
Any of those possibilities would be a great improvement in my eyes.
Ideally, it would also be possible to collaborate together on some of the lists.