It would be cool if you could share individual lists or groups containing lists with your friends and both be able to add to them. This could be done through iCloud Family Sharing or through the addition of a friends list.
Using force touch, you can select a list or group and share to others as an invite to allow them to edit the lists. Any changes made are notified to the other members.
When I’m hanging with other people, in order for them to see my lists, I have to AirPlay my phone screen to the TV in order for them to see my lists.